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COPYRIGHT DEPOSUft 




MARCONI WIRELESS TELEGRAPH STATION, CLIFDEN, IRELAND 

Photographed at night while sending a message across the Atlantic. 

The terrific snapping of the electric discharge is heard by one 
standing near the station, but no light is seen. The strange light 
given out from the network of wires is invisible to the eye, but is 
caught by the photographic plate. 




THE SAME STATION PHOTOGRAPHED BY DAYLIGHT 



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THE STORY OF 
REAT INVENTIONS 



BY 

ELMER ELLSWORTH BURNS 

Instructor in Physics in the 
Joseph Medill High School, Chicago 



WITH MANY ILLUSTRATIONS 




HARPER & BROTHERS PUBLISHERS 

NEW YORK AND LONDON 
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Copyright, 1910, by Harper & Brothers 

Published November, iqio. 
Printed ut the United States of America 



©CI.A2753G3 



CONTENTS 

CHAPTER I 
THE AGE OF ARCHIMEDES 
Archimedes the first great inventor.— The battle of Syracuse. — Archi- 
medes' principle. — Inventions of the ancient Greeks . . . Page i 

CHAPTER II 
THE AGE OF GALILEO 
Galileo and the battle for truth. — The pendulum clock. — Galileo's ex- 
periment with falling shot. — The telescope. — Galileo's struggle. — 
Torricelli and the barometer. — Otto von Guericke and the air-pump. — 
Robert Boyle and the pressure of air and steam. — Pascal and the 
hydraulic press. — Newton. — Gravitation. — Colors in sunlight . Page 9 

CHAPTER III 
THE EIGHTEENTH CENTURY 
James Watt and the steam-engine. — The first steam-engine with a piston. 
— Newcomen's engine. — Watt's engine. — Horse-power of an engine. — 
The Leyden jar. — Conductors and insulators. — Two kinds of electric 
charge. — Franklin's kite experiment. — The lightning-rod. — Galvani 
and the electric current. — Volta and the electric battery . . Page 34 

CHAPTER IV 
FARADAY AND THE FIRST DYNAMO 
Count Rumford. — Count Rumford's experiment with the cannon. — Davy. 
— Faraday's electrical discoveries. — Oersted and electromagnetism. — 
Ampere. — Arago. — Faraday's first electric motor. — An electric current 
produced by a magnet. — Detecting and measuring an electric current. 
— An electric current produced by the magnetic field of another cur- 
rent. — Faraday's dynamo. — A wonderful law of nature . , Page 55 

V 



CONTENTS 



CHAPTER V 
GREAT INVENTIONS OF THE NINETEENTH CENTURY 
Electric batteries. — The dry battery. — The storage battery. — The dy- 
namo. — Siemens' dynamo. — The drum armature. — Edison's compound- 
wound dynamo. — Electric power. — The first electric railway. — Electric 
lighting. — The telegraph. — Duplex telegraphy. — The telephone. — The 
phonograph. — Gas-engines. — The steam locomotive. — How a locomo- 
tive works. — The turbine Page 88 

CHAPTER VI 

THE TWENTIETH-CENTURY OUTLOOK 

Air-ships. — The aeroplane. — How the Wright aeroplane is kept afloat. — 
Submarines. — Some spinning tops that are useful. — The monorail-car. 
— Liquid air and the greatest cold. — The electric furnace and the 
greatest heat. — The wireless telegraph — The wireless telephone. — 
Wonders of the alternating current. — X-rays and radium . Page 173 

APPENDIX 
Brief notes on important inventions . Page 237 

Index Page 247 



ILLUSTRATIONS 



FIG. PAGE 

MARCONI WIRELESS-TELEGRAPH STATION, CLIFDEN, IRELAND ) 

y Frontispiece 
THE SAME STATION PHOTOGRAPHED BY DAYLIGHT . . ) 

I THE BATTLE OF SYRACUSE 3 

2 — Galileo's pendulum clock ii 

3 AN AIR THERMOMETER 14 

4 TORRICELLl'S EXPERIMENT I9 

5 GUERICKE's air-pump 22 

6 — guericke's water barometer 24 

7 — A lift-pump 25 

8 A SIMPLE hydraulic PRESS 26 

9 HOW AN HYDRAULIC PRESS WORKS . 28 

10 AN HYDRAULIC PRESS WITH BELT-DRIVEN PUMP 29 

II — Newton's experiment with the prism -32 

12 — papin's engine . 36 

13 the newcomen engine, in repairing which watt was led 

to his great discoveries 39 

14 CYLINDER OF WATT's STEAM-ENGINE 41 

15 a fly-ball governor 42 

16 a leyden jar 43 

17 — franklin's kite experiment 47 

18 volta explaining his electric battery to napoleon bona- 
PARTE 52 

19— THE FIRST ELECTRIC BATTERY 54 

20 COUNT RUMFORD's EXPERIMENT WITH THE CANNON, MAKING 

WATER BOIL WITHOUT FIRE 60 

21 oersted's EXPERIMENT 66 

22 A COIL WITH A CURRENT FLOWING THROUGH IT ACTS LIKE A 

MAGNET 67 

23 A BAR OF SOFT IRON WITH A CURRENT FLOWING AROUND IT BE- 
COMES A MAGNET 67 

24 TWO COILS WITH CURRENTS FLOWING IN THE SAME DIRECTION 

ATTRACT EACH OTHER 68 

25 TWO COILS WITH CURRENTS FLOWING IN OPPOSITE DIRECTIONS 

REPEL EACH OTHER 68 

26 ARAGO'S EXPERIMENT ,,.,,,. 70 

vii 



ILLUSTRATIONS 



FIG. PAGE 

27 one pole of a magnet spins round a wire through which 

an electric current flows 7 1 

28 when a magnet is thrust into a coil of wire it causes a 

current to flow in the coil, but the current flows 

only while the magnet is moving 73 

29 a coil of wire around a compass-needle 74 

30 — Faraday's induction-coil , . , 76 

31 historical apparatus of faraday in the royal institution 77 

32 — Faraday's first dynamo 78 

33 — Faraday's laboratory, where the first dynamo was 

MADE 79 

34 — the first transformer 80 

35 — THE "magnetic field" is the space around a magnet 

in which it will attract iron 81 

36 — magnetic field of a horseshoe magnet 81 

37 a daniell cell 90 

38 a gravity cell 9i 

39 showing what is in a dry battery 92 

40 a storage battery, showing the " grids " 94 

41 a storage-battery plate made from a sheet of lead . . 95 

42 sturgeon's ELECTROMAGNET 97 

43 AN ELECTROMAGNET WITH MANY TURNS OF INSULATED WIRE . 98 

44 AN ELECTROMAGNET LIFTING TWELVE TONS OF IRON ... 99 

45 A DYNAMO WITH SIEMENS' ARMATURE lOI 

46 RING ARMATURE I02 

47 FIRST DYNAMO PATENTED IN THE UNITED STATES . . . . IO3 

48 A DRUM ARMATURE, SHOWING HOW AN ARMATURE OF FOUR 

COILS IS WOUND 104 

49 A SERIES-WOUND DYNAMO I06 

50 A SHUNT-WOUND DYNAMO I07 

51 A COMPOUND-WOUND DYNAMO I08 

52 ONE OF EDISON's FIRST DYNAMOS IO9 

53 A DYNAMO MOUNTED ON THE TRUCK OF A RAILWAY CAR . . . IIO 

54 FIRST ELECTRIC LOCOMOTIVE II3 

55 FIRST EDISON ELECTRIC LOCOMOTIVE . . II5 

56 EDISON's FIRST PASSENGER LOCOMOTIVE II7 

57 FIRST COMMERCIAL ELECTRIC RAILWAY II9 

58 — EDISON, America's greatest inventor, at work in his 

LABORATORY 122 

59 EDISON's FAMOUS HORSESHOE PAPER-FILAMENT LAMP OF 187O. 123 

60 FIRST COMMERCIAL EDISON ELECTRIC-LIGHTING PLANT; IN- 
STALLED ON THE STEAMSHIP "COLUMBIA" IN MAY, 1880 . 125 
6j A TELEGRAPH SOUNDER . 129 

viii 



ILLUSTRATIONS 



FIG. PAGE 

62 — morse's first telegraph instrument 131 

63 — A telegraphic circuit with relay and sounder. . . , 132 

64 — A simple telegraphic circuit 133 

65 FIRST telegraph INSTRUMENT USED FOR COMMERCIAL WORK . I35 

66 HOW TWO MESSAGES ARE SENT OVER ONE WIRE AT THE SAME 

TIME 137 

67 HOW TWO MESSAGES ARE SENT OVER ONE WIRE AT THE SAME 

TIME, BRIDGE METHOD I39 

68 FIRST BELL TELEPHONE RECEIVER AND TRANSMITTER . . . 142 

69 A TELEPHONE RECEIVER I43 

70 TWO RECEIVERS USED AS A COMPLETE TELEPHONE .... 145 

71 CARBON-DUST TRANSMITTER 146 

72 THE PHONAUTOGRAPH, A FORERUNNER OF THE PHONOGRAPH . 149 

73 EDISON'S first PHONOGRAPH AND A MODERN INSTRUMENT . 150 

74 to 77 THE FOUR-CYCLE GAS-ENGINE 152 

78 two-cycle gas-engine. crank and connecting-rod are 

enclosed with the piston 1 54 

79 selden "explosion buggy," forerunner of the modern 

automobile 1 55 

80 some early locomotives 1 58 

81 how a locomotive works 161 

82 — hero's engine 164 

83 AN undershot water-wheel WITH CURVED BLADES . . . 165 

84 AN OVERSHOT WATER-WHEEL 1 66 

85 DE LAVAL STEAM-TURBINE 167 

86 A MODERN STEAM-TURBINE WITH TOP CASING RAISED SHOWING 

BLADES 168 

87 DIAGRAM OF TURBINE SHOWN IN FIG. 86 169 

88 A STEAM-TURBINE THAT RUNS A DYNAMO GENERATING I4,000 

ELECTRICAL HORSE-POWER 170 

89 BRITISH ARMY AIR - SHIP " NULLI SECUNDUS" READY FOR 

FLIGHT 176 

90 BASKET, MOTOR, AND PROPELLER OF THE BRITISH ARMY AIR- 
SHIP "nULLI SECUNDUS " 178 

91 A ZEPPELIN AIR-SHIP 181 

92 COUNT ZEPPELIN'S " DEUTSCHLAND," THE FIRST AIR-SHIP IN 

REGULAR PASSENGER SERVICE 182 

93 THE BALDWIN AIR-SHIP USED IN THE UNITED STATES ARMY . . 183 

94 IN FULL FLIGHT 185 

95 WRIGHT AIR-SHIP IN FLIGHT 187 

96 HOW THE WRIGHT AIR-SHIP IS KEPT AFLOAT 189 

97 THE SEAT AND MOTOR OF THE WRIGHT AEROPLANE .... 191 

98 THE BLERIOT MONOPLANE 192 

Ik 



ILLUSTRATIONS 



FIG. PAGE 

99 — THE "plunger" 195 

100 U, S. SUBMARINE " SHARK " READY FOR A DIVE I97 

lOI FIRST SUBMARINE CONSTRUCTED IN THE UNITED STATES. IT 

WENT TO THE BOTTOM WITH SEVEN MEN, WHO WERE 

DROWNED 198 

102 HOW MEN IN A SUBMARINE SEE WHEN UNDER THE WATER . 199 

103 A TOP THAT SPINS ON A STRING 200 / 

104 A CAR THAT RUNS ON ONE RAIL 202 . 

105 MANUFACTURING DIAMONDS FIRST OPERATION 207 ' 

106 MANUFACTURING DIAMONDS SECOND OPERATION .... 209 ' 

107 MANUFACTURING DIAMONDS THIRD OPERATION 211 ' 

108 MARCONI AND HIS WIRELESS - TELEGRAPH SENDING AND RE- \ 

CEIVING INSTRUMENTS 215 ! 

109 DIAGRAM OF WIRELESS-TELEGRAPH SENDING APPARATUS . . 217 

no DIAGRAM OF MARCONI WIRELESS-TELEGRAPH RECEIVING 

APPARATUS 218 

III RECEIVER OF BELL's PHOTOPHONE 223 

112 A GAS FLAME IS SENSITIVE TO ELECTRIC WAVES .... 224 

113 CAPTAIN INGERSOLL ON BOARD THE U. S. BATTLE - SHIP 

"CONNECTICUT" USING THE WIRELESS TELEPHONE . . 226 
114 INCANDESCENT ELECTRIC LAMP LIGHTED THOUGH NOT CON- 
NECTED TO ANY BATTERY OR DYNAMO 229 

115 AN ELECTRIC DISCHARGE AT A PRESSURE OF 12,000,000 VOLTS, 

A CURRENT OF 80O AMPERES IN THE SECONDARY COIL . . 23O 

116 AN ELECTRIC DISCHARGE SIXTY-FIVE FEET IN LENGTH . . 23 1 

117 A PHYSICIAN EXAMINING THE BONES OF THE ARM BY MEANS 

OF X-RAYS 233 

118 X-RAY PHOTOGRAPH OF THE EYE 234 

119 PHOTOGRAPH MADE WITH RADIUM 235 



INTRODUCTORY NOTE 

GREAT inventions are a never-failing source of interest 
to all of us, and particularly to the boy in his teens. 
The dynamo, the electric motor, the telegraph, with and 
without wires, the telephone, air- ships, and many other 
inventions excite in him an interest which is deeper than 
mere curiosity. He wants to know how these things work, 
and how they were invented. The man is so absorbed in 
the present that he cares little for the past. Not so with 
the boy. He cares for the history of inventions, and in 
this he is wiser than the man, for it is only by a study of 
its origin and growth that we can understand the larger 
significance of a great invention. 

Great inventions have their origin in great discoveries. 
The story of great inventions, therefore, includes the story 
of the discoveries out of which they have arisen. The 
stories of the discoveries and the inventions are inseparable 
from the lives of the men who made them, and so we must 
deal with biography, which in itself is of interest to the 
boy. Such a story is the story of physical science in the 
service of humanity. 

The interest of the youth in great inventions is unques- 
tioned. Shall we stifle this interest by overemphasis of 

xi 



INTRODUCTORY NOTE 



technical detail, or shall we minister to it as a thing vital 
in the life of the youth of to-day ? 

A few sentences quoted from G. Stanley Hall will indi- 
cate the author's point of view. "The youth is in the 
humanist stage. Nature is sentiment before it becomes 
idea or formula or utility." "The heroes and history 
epochs of each branch [of science] add another needed 
quality to the still so largely humanistic stage." "Anew 
discovery, besides its technical record, involves the added 
duty of concise and lucid popular statement as a tribute 
to youth." The need of a "concise and lucid popular 
statement" of the rise of the great inventions which 
form the material basis of our modern civilization and 
all of which are new to the young mind, has no doubt 
been keenly felt by others as it has been by the author. 
The story of our great inventions has been told in sundry 
volumes for adult readers, but nowhere has this story, alive 
with human interest, been told in a form suited to the 
young. It was the realization of this need growing out of 
years of experience in teaching these branches that led the 
author to attempt the task of writing the story. 

The purpose of this book is to tell in simple language 
how our great inventions came into being, to depict the life- 
struggles of the men who made them, and, in the telling of 
the story, to explain the working of the inventions in a 
way the boy can understand. The stories which are here 
woven together present the great epochs in the history of 
physics, and are intended to give to the young reader a 
connected view of the way in which our great inventions 
have arisen out of scientific discovery on the one hand, and 

xii 



INTRODUCTORY NOTE 



conditions which we may call social and economic on the other 
hand. If the book shall appeal to young readers, and lead 
them to an appreciation of the meaning of a great inven- 
tion, the author will feel that his purpose has been achieved. 

The author is deeply indebted to Dr. Charles A. McMurry 
and Prof. Newell D. Gilbert, of the Northern Illinois State 
Normal School; Profs. C. R. Mann and R. A. Millikan, of 
the University of Chicago; and Prof. John F. Woodhull, of 
Columbia University, for reading the manuscript and offer- 
ing valuable suggestions. Acknowledgment is further 
made here of valuable aid in collecting material for illus- 
trations and letter-press. Such acknowledgment is due 
to Prof. A. Gray, University of Glasgow; Prof. Antonio 
Favaro, Royal University of Padua; Prof. A. Zammarchi, 
Brescia, Italy; Mr. Nikola Tesla; the Royal Institution, 
London; McClure's Magazine; The Technical World Maga- 
zine; The Scientific American; the Ellsworth Company; 
Commonwealth-Edison Company; Association of Edison 
Illuminating Companies; Electric Controller and Supply 
Company; Kelley-Koett Manufacturing Company; Watson- 
Stillman Company ; Gould Storage Battery Company ; Thor- 
darson Electric Company ; the Westinghouse Machine Com- 
pany; Marconi Wireless Telegraph Company of America, 
and the Siemens-Schuckert Werke, Berlin. 

The drawings illustrating Faraday's experiments are 
from exact reproductions of Faraday's apparatus, made 
by Mr. Joseph G. Branch, author of Conversations on Elec- 
tricity, and are reproduced by his kind permission. 

E. E. B. 

Chicago, June, 19 lo. 



THE 
STORY OF GREAT INVENTIONS 



THE 
STORY OF GREAT INVENTIONS 

Qiaptcr I 

THE AGE OF ARCHIMEDES 

Archimedes^ the First Great Inventor 

ARCHIMEDES, the first great inventor, lived in Syracuse 
/i more than two thousand years ago. Syracuse was a 
Greek city on the island of Sicily. The King of Syracuse, 
Hiero, took great interest in the discoveries of Archimedes. 
One day Archimedes said to King Hiero that with his own 
strength he could move any weight whatever. He even 
said that, if there were another earth to which he could go, 
he could move this earth wherever he pleased. The King, 
full of wonder, begged of him to prove the truth of his state- 
ment by moving some very heavy weight. Whereupon 
Archimedes caused one of the King's galleys to be drawn 
ashore. This required many hands and much labor. Hav- 
ing manned the ship and put on board her usual loading, he 
placed himself at a distance and easily moved with his hand 
the end of a machine which consisted of a variety of ropes 



THE STORY OF GREAT INVENTIONS 

and pulleys, drawing the ship over the sand in as smooth 
and gentle a manner as if she had been under sail. The 
King, quite astonished, prevailed with Archimedes to make 
for him all manner of machines which could be used either 
for attack or defence in a siege. 

The Battle of Syractise 

During the life of King Hiero Syracuse had no occasion 
to use the war machines of Archimedes. The grandson of 
King Hiero, who succeeded to the throne, was a tyrant. He 
attempted to throw off the sovereignty of Rome and en- 
tered into an alliance with Carthage. His cruelty toward 
his own people was so great that, after a short reign, he was 
assassinated. There was anarchy in Syracuse for a time, 
the Roman and anti-Roman parties striving for supremacy. 
The anti-Roman party gaining possession of the city, the 
Romans, in order to bring Syracuse again into subjection, 
prepared for an attack by sea and land. Then it was that 
Syracuse had need of the war machines made by Archimedes 
(Fig. i). 

The Romans came with a large land force and a fleet. 
They were sure that within five days they could conquer the 
city. But there are times when one man with brains is 
worth more than an army. In the battle which followed, 
Archimedes with his inventions was more than a match for 
the Romans. 

The city was strong from the fact that the wall on one side 
lay along a chain of hills with overhanging brows; on the 
other side the wall had its foundation close down bv the sea. 




FIG. I THE BATTLE OF SYRACUSE 

The city defended by the inventions of Archimedes. 



THE STORY OF GREAT INVENTIONS 

A fleet of sixty ships commanded by Marcellus bore down 
upon the city. The ships were full of men armed with bows 
and slings and javelins with which to dislodge the men who 
fought on the battlements. Eight ships had been fastened 
together in pairs. These double vessels were rowed by the 
outer oars of each of the pair. On each pair of ships was a 
ladder four feet wide and of a height to reach to the top of 
the wall. Each side of the ladder was protected by a railing, 
and a small roof-like covering, called a penthouse, was fast- 
ened to the upper end of the ladder. This covering served 
to protect the soldiers until they could reach the top of the 
wall. They thought to bring these double ships close to 
shore, raise the ladders by ropes and pulleys until they rest- 
ed against the wall, then scale the wall and capture the city. 

But Archimedes had crossbows ready, and, when the ships 
were still at some distance, he shot stones and darts at the 
enemy, wounding and greatly annoying them. When these 
began to carry over their heads, he used smaller crossbows of 
shorter range, so that stones and darts fell constantly in their 
midst. By this means he checked their advance, and finally 
Marcellus, in despair, was obliged to bring up his ships under 
cover of night. But when they had come close to land, and 
so too near to be hit by the crossbows, they found that 
Archimedes had another contrivance ready. He had pierced 
the wall as high as a man's head with many loopholes which 
on the outside were about as big as the palm of the hand. 
Inside the wall he had stationed archers and men with cross- 
bows to shoot down the marines. By these means he not 
only baffled the enemy, but killed the greater number of 
them. When they tried to use their ladders, they discovered 

4 



THE AGE OF ARCHIMEDES 



that he had cranes ready all along the walls, not visible at 
other times but which suddenly reared themselves above the 
wall from the inside and stretched their beams far over the 
battlements, some of them carrying stones weighing about 
five hundred pounds, and others great masses of lead. So, 
whenever the ships came near, these beams swung round on 
their pivots and by means of a rope running through a 
pulley dropped the stones upon the ships. The result was 
that they not only smashed the ships to pieces, but killed 
many of the soldiers on board. 

Another machine made by Archimedes was an "iron 
hand" or grappling-hook swung on a chain and carried by a 
crane. The hook was dropped on the prow of a ship, and 
when it had taken hold the ship was lifted until it stood on 
its stem, then quickly dropped, causing it either to sink or 
ship a great quantity of water. 

With such machines, unknown before, Archimedes drove 
back the enemy. On the landward side similar machines 
were used. The Romans were reduced to such a state of 
terror that "if they saw but a rope or a stick put over the 
walls they cried out that Archimedes was levelling some 
machine at them and turned their backs and fled." 

After a long siege, however, hunger forced the Syracusans 
to surrender. Marcellus so admired the genius of Archi- 
medes that he gave orders that he should not be injured. 
Yet, in the sack of the city which followed, Archimedes was 
slain by a Roman soldier. 

The Roman historian Livy records that "Archimedes, 
w^hile intent on some figures which he had made in the dust, 
although the confusion was as great as could possibly be, 

5 



THE STORY OF GREAT INVENTIONS 

was put to death by a soldier who did not know who he was ; 
that Marcellus was greatly grieved at this, and that pains 
were taken about his funeral, while his relations also were 
carefully sought and received honor and protection on ac- 
count of his name and memory." 

Archimedes' Principle 

Hiero, when he became King of Syracuse, decreed that a 
crown of gold, of great value, should be placed in a certain 
temple as an offering to the gods, and sent to a manufacturer 
the correct weight of gold. In due time the crown was 
brought to the King, and a beautiful piece of work it was. 
The weight of the crown was the same as that of the gold, 
but a report was circulated that some of the gold had been 
taken out and silver supplied in its place. Hiero was angry, 
but knew no method by which the theft might be detected. 
He therefore requested Archimedes to give the matter his 
attention. 

While trying to solve this problem Archimedes went one 
day to a bath. As he got into the bath-tub he saw that as 
his body became immersed the water ran out of the tub. 
He quickly saw how he could solve the problem, leaped out 
of the bath in joy, and, running home naked, cried out with 
a loud voice "Eureka! eureka!" (I have found it! I have 
found it!) 

Using a piece of gold and a piece of silver, each equal in 
weight to the crown, and a large vase full of water, he 
proved that the crown was not pure gold, and found how 
much silver had been mixed with the gold. 

The incident of the golden crown may have been the 

6 



THE AGE OF ARCHIMEDES 



starting-point of Archimedes' study of solid bodies when 
immersed in fluids. Every one knows that a boy can lift 
a heayy stone under water that he could not lift out of 
water. The stone seems lighter when in the water. A diver 
with his lead-soled shoes could scarcely walk on land, but 
walks easily under water. When the diver comes up, the 
place where he was immediately becomes filled with water. 
Now, whatever that water weighs which fills the diver's 
place, just that much weight will the diver lose when he goes 
down. What is true of the diver is true of the stone or of 
any object under water. The stone when in the water loses 
just as much weight as the weight of the water that would 
fill its place. This is the fact which was discovered by 
Archimedes and which is called ''Archimedes' Principle." 

It is said by an ancient author that Archimedes invented 
more than forty machines. Of these the best known are 
the block and tackle, the endless screw (worm gear), and the 
water snail, or Archimedean screw. Yet his delight was not 
in his machines, but in his mathematics. Though he had 
invented machines to please his king, he regarded such work 
as trifling, and took little interest in the common needs of 
life. 

Inventions of the Ancient Greeks 

The common needs of life are to-day the chief concern of 
the greatest men, and so we find it hard to sympathize with 
this view of Archimedes. His view, however, was that of 
other learned men of his time, that the common needs of 
life are beneath the dignity of the scholar, and so we can see 
why the Greeks made so few great inventions. 

7 



THE STORY OF GREAT INVENTIONS 

Hero, who lived a century later than Archimedes, invented 
a steam-engine, which, however, was only a toy. A water- 
clock, in which the first cog-wheels were used, was invented 
by another Greek named Ktesibus, who also invented the 
force-pump. The suction-pump was known in the time of 
Aristotle, who lived about a century before the time of 
Archimedes, but the inventor is unknown. 

Concerning electricity, the Greeks knew very little. They 
knew that amber when rubbed will attract light objects, 
such as dust or chaff. Amber was called by the Greeks 
"electron," because it reflected the brightness of the sun- 
light, and their name for the sun was "Elector." From the 
Greek name for amber we get our word "electricity." 

The Greeks possessed scarcely more knowledge of magnets 
than of electricity. In fact, their ideas of magnets cannot 
be called knowledge, for they consisted chiefly of legends. 

They told of the shepherd Magnes, who, while watching 
his flock on Mount Ida, suddenly found the iron ferrule of 
his staff and the nails of his shoes adhering to a stone; that, 
later, this stone was called, after him, the "Magnes stone," 
or "Magnet." 

They told impossible stories of iron statues being sus- 
pended in the air by means of magnets, and of ships sailing 
near the magnetic mountains when every nail and piece of 
iron in the ship would fly to the mountain, leaving the ship 
a wreck upon the waves. 



Chapter II 

THE AGE OF GALILEO 

Galileo and the Battle for Trtith 

FOR eighteen centuries after the time of Archimedes 
no inventions of importance were made. Men sought 
for truth where truth could not be found. They looked 
within their mouldy manuscripts and asked, ''What do the 
great philosophers say ought to happen?" instead of look- 
ing at nature and asking, "What does happen ?" And when 
a man arose who dared to doubt the authority of the old 
masters and turn to nature to find out the truth, all the 
weapons at the command of the old school were hurled 
against him. 

Let us, at this distance, blame neither the one side nor 
the other. The conflict was inevitable. It was an acci- 
dent of history that the brunt of the attack fell upon a 
man born in Italy in 1564, and that the battle was fought 
chiefly in the "Eternal City," from which centuries before 
had marched the legions that conquered the world. 

The boy, Galileo, who was to become the central figure 
of the great conflict, was talented in many ways. In lute- 
playing his skill excelled that of his father, who was one of 
the noted musicians of his day. His skill in drawing was 

9 



THE STORY OF GREAT INVENTIONS 

such that noted artists submitted, their work to him for 
criticism. He wrote essays on the works of Dante and 
other classical writers. He amused his boy companions by 
constructing toy machines which, though ingenious, did not 
always work. 

His preference was for mechanics, but, as this subject 
offered little prospect of profitable work, he took up the 
study of medicine in accordance with his father's wishes. 

In his eighteenth year he entered the University of Pisa. 
Here he found men who refused to think for themselves, 
but decided every question by referring to what the ancient 
philosophers said. Galileo could not endure such slavish 
submission to authority. So strongly did he assert himself 
that he was nicknamed **The Wrangler," and, by his wrang- 
ling, he lost a scholarship in the university. 

He neglected his medical studies and secretly studied 
mathematics. His father, learning of this, consented to his 
becoming a mathematician. Thus he followed his bent, 
though it seemed to lead directly to poverty. 

The Fendiilum Clock 

It was while a student at the University of Pisa that 
he discovered a law of pendulums which makes possible 
our pendulum clocks. While at his devotions in the cathe- 
dral, he observed the swinging of the bronze lamp which 
had been drawn back for lighting. Timing its swinging by 
means of his pulse, the only timepiece in his possession, he 
found that the time of one swing remained the same, though 
the length of the swing grew smaller and smaller. This 

10 




FIG. 2 GALILEO S PENDULUM CLOCK 

It had only one hand, which is not shown in the picture, 



THE STORY OF GREAT INVENTIONS 

discovery led to his invention of an instrument for physi- 
cians' use in timing the pulse. About fifty years later he 
invented the pendulum clock (Fig. 2). 

Lack of funds compelled him to leave the university with- 
out completing his course. He returned to the parental 
roof and continued his scientific studies. The writings of 
Archimedes were his favorite study. With Archimedes' 
famous experiment on King Hiero's crown as a starting- 
point, he discovered the laws of floating bodies, which ex- 
plain why a ship or other object floats on water, and in- 
vented a balance for weighing objects in water. 

But such employment won nothing more substantial than 
honor and fame. Food and clothing were needed. For 
two years he strove without success to secure employment. 
At the end of that time he was appointed professor of mathe- 
matics in the University of Pisa at the magnificent salary 
of sixty scudi (about sixty-three dollars) per year. ''But 
any port in a storm; and in Galileo's needy circumstances 
even this wretched salary was not to be rejected." More- 
over, he could add somewhat to his income by private 
tutoring. 

Galileo's Experiment with Falling Shot 

While teaching at the University of Pisa, he performed 
his famous experiment of dropping from the top of the 
leaning tower two shot, one weighing ten pounds, the other 
one pound. Now, according to Aristotle, the ten-pound 
shot should fall in one-tenth the time required by the one- 
pound shot. But the assembled company of professors and 
students saw the two shot start together, fall together, and 

12 



THE AGE OF GALILEO 



strike the ground at the same instant, and still refused to 
believe their own eyes. They continued to affirm that a 
weight of ten pounds would reach the ground in a tenth of 
the time taken by a one-pound weight, because they were 
able to quote chapter and verse in which Aristotle assured 
them that such is the fact. Thus Galileo made enemies of 
the other professors, but for a time they could do nothing 
more than annoy him. 

About this time Galileo incurred the wrath of the Grand 
Duke of Tuscany, from whom he had received his appoint- 
ment. He was commissioned to examine a machine in- 
vented by a nephew of the Grand Duke for the purpose of 
cleaning harbors. Galileo plainly said that the machine 
was worthless. It was tried, and his opinion proved true. 
But like the kings of olden time who killed the bearer of 
evil tidings even though the tidings were true, his enemies 
made his position so unpleasant that he resigned. 

He had neither employment nor money. His father's 
death occurring about this time, threw upon him the care 
of a mother, a worthless brother, and two sisters. In his 
distress he sought help from a friend, and secured an ap- 
pointment as professor of mathematics in the University of 
Padua . His salary was one hundred and eighty florins (about 
ninety-five dollars), while other professors received more 
than ten times as much. 

While at Padua, Galileo was busy inventing. He in- 
vented the sector, which is to be found in most cases of 
mathematical instruments and is used in certain kinds of 
drawing. He also invented an air thermometer (Fig. 3), 
the first instrument for measuring temperature. 

13 





AIR THERMOMETER 



FIG. 3 AN 

When the air in the bulb grows cooler it contracts, and the air outside 
forces the water up the tube. When the air in the bulb grows warmer it 
expands and forces the water down in the tube. 



THE AGE OF GALILEO 



In 1604 there appeared a new star of great brilliancy. 
It continued to shine with varying brightness for eighteen 
months, and then vanished. This was a strange event, and 
Galileo made use of it. He proved that the new star must 
lie among the most distant of the heavenly bodies, and this 
fact did not agree with Aristotle's view that the heavens 
are perfect, and therefore never change. A heated con- 
troversy followed, and Galileo came out boldly in favor 
of the theory that the earth revolves about the sun, the 
prevailing notion then being that the earth does not 
move, but that the sun and other heavenly bodies revolve 
around it. 

The Telescope 

In 1609 Galileo learned of a discovery that was to be of 
great value to the world, but a source of untold trouble to 
himself. An apprentice of a Dutch optician, while playing 
with spectacle lenses, chanced to observe that if two of 
the lenses were placed in a certain position objects seen 
through them appeared much nearer. Galileo, learning of 
this, set to work to construct a spy - glass, applying his 
knowledge of light. In one day he had constructed such 
an instrument, in which he used two lenses like the lenses 
of the modern opera - glass. Thus, while the Dutchman's 
discovery was by accident, Galileo's was by reasoning, and 
was the more fruitful, as we shall see. 

Galileo continued improving his telescope until he had 

made one which would magnify thirty times. He was the 

first to apply the telescope to the study of the heavenly 

bodies. The most startling of his discoveries was that of 

2 15 



THE STORY OF GREAT INVENTIONS 

the moons of the planet Jupiter, which he called new 
planets. 

This aroused the fury of his enemies, who ridiculed the 
idea of there being new planets; **for," they said, "to see 
these planets they must first be put inside the telescope." 
The excitement was intense. Poets chanted the praise of 
Galileo. A public fete was held in his honor. One of his 
pupils was imprisoned in the tower of San Marco, where 
he had gone to make observations with his telescope, and 
could not escape until the crowd had satisfied their curiosity. 
Some of the philosophers refused to look lest they should 
see and be convinced. 

Galileo's Strtiggle 

His enemies sought to steal from him the honor of his 
discoveries. Some claimed to have made the discoveries 
before Galileo did. Others claimed that his discoveries 
were false, that their only use was to gratify Galileo's vanity 
and thirst for gold. In these trying times the friendship of 
the great astronomer Kepler warded off some of the most 
exasperating attacks. 

Galileo's fame spread throughout Europe. Students came 
in great numbers, so that he had little leisure left for his 
own studies. He therefore decided to leave Padua, and 
secured an appointment as mathematician and philosopher 
to the Grand Duke of Tuscany. This appointment took 
him to Florence. It was here that an incident occurred 
that marked the beginning of a persecution which continued 
to the end of his life. 

As we read the story of this conflict let us remember that 

i6 



THE AGE OF GALILEO 



it was not primarily a conflict between the Roman Catholic 
Church and Galileo. It was a conflict of principles. On 
the one side were arrayed those who said that men should 
always believe as the ancient writers did; on the other, 
those who said men should think for themselves. In the 
first party were most of the university professors and others 
who dreaded the introduction of new beliefs, whether in 
religion or science. In the second party were Galileo and 
a small band of devoted followers. 

At a dinner at the table of the Grand Duke in Pisa the 
conversation turned on the moons of Jupiter. Some praised 
Galileo. Others condemned him, saying that the Holy 
Scriptures were opposed to his theory of the motion of the 
earth. A friend reported the incident to Galileo, and he 
replied to the arguments of his opponents in a letter which 
was made public. No doubt the sting of his sarcasm made 
his enemies more bitter. He admitted that the Scriptures 
cannot lie or err, but this, he said, does not hold good of 
those who attempt to explain the Scriptures. In another 
letter, he quoted with approval a saying of Cardinal Ba- 
ronius, "The Holy Spirit intended to teach us in the Bible 
how to go to Heaven, not how the heavens go." 

The first shot had been fired. The battle was on, and 
the Church, because it possessed the most powerful weap- 
ons of attack, was used by the combined forces to break 
the power of Galileo's reasoning. He went to Rome to 
make his defence, but was commanded by the Holy Office 
not to hold or teach that the sun is immovable, and that 
the earth moves about the sun. 

During another visit to Rome there was shown to Galileo 

17 



THE STORY OF GREAT INVENTIONS 

an instrument which, it was said, would show a flea as large 
as a cricket. Galileo recalled that some years before he 
had so arranged a telescope that he had seen flies which he 
said looked as big as a lamb, and were covered all over with 
hair. This was the first microscope. Galileo quickly im- 
proved the instrument, and soon his microscopes were in 
great demand. 

In violation of the decree of the Church, to which he had 
submitted, he published his most famous work in which 
he defended the theory that the earth moves about the 
sun. The book was the outcome of his life-work, but the 
Church believed it dangerous. He was summoned to 
Rome. Confined to a sick-bed, he pleaded for delay, which 
was granted. Before he recovered, however, the summons 
was made imperative. He must go to Rome, or be carried 
in irons. He went in a litter, carried by servants of the 
Grand Duke. In Rome he was to appear before the In- 
quisition. There he was treated with a consideration never 
before accorded to a prisoner of the Inquisition. Nor was 
he subjected to torture, as has been stated by some. He 
was found guilty of teaching the doctrine that the sun does 
not move, and that the earth moves about the sun. He 
was compelled to recant, and sentenced to the prison of 
the Holy Office and, by way of penance, to repeat once a 
week for three years the seven penitential Psalms. 

He yielded without reserve to the decree of the Inquisi- 
tion, renounced his ** errors and heresies," and, with his 
hand on the Bible, took oath never again to teach the for- 
bidden doctrine. 

And now, though a shattered old man of seventy-four, 

i8 



THE AGE OF GALILEO 



enjoined to silence on the chief results of his life-work, 
nothing could quench his devotion to science. In these 
last years, he published a new book which, with his earlier 
work, entitles him to be regarded as the founder of the 
science of mechanics. 

In his study of machines Galileo found that no machine 
will do work of itself. Whenever a machine is at work, a 
man or a horse, or some other power, is at work upon the 
machine. In no case will a machine do work without re- 
ceiving an equal amount of work. 

Torricelli and the Barometer 

Galileo had a pump which he found 
would not work when the water was 
thirty-five feet below the valve. He 
thought the pump was injured, and 
sent for the maker. The maker as- 
sured him that no pump would do 
better. This led Torricelli, one of 
Galileo's pupils, to the discovery of 
the barometer. Men had said that 
water rises in a pump because nature 
abhors a vacuum. Torricelli believed 
that air-pressure and not nature's 
"horror of a vacuum" is the cause 
of water rising in a pump. He in- 
vented the barometer to measure air- 
pressure. 

The first barometer was a glass tube filled with quick- 
silver or mercury (Fig. 4). The tube was closed at the 

19 




FIG. 4 TORRICELLI S 

EXPERIMENT 



THE STORY OF GREAT INVENTIONS 

upper end, and the lower end, which was open, dipped in 
a dish of mercury. He allowed the tube to stand, and saw 
that the height of the mercury changed. This he believed 
was because the air - pressure changed. Wind, Torricelli 
said, is caused by a difference of air-pressure, which is due 
to unequal heating of the air. For this reason a cool breeze 
blows from the mountain top to the heated valley, or from 
sea to land on a summer day. 

Otto Von Gaericke and the Air-Ptjmp 

About this time a German burgomaster, Otto von Guericke, 
of Magdeburg, was performing experiments on air-pressure. 
The Thirty Years' War had been raging for thirteen years. 
The Swedish King, Gustavus Adolphus, had landed in Ger- 
many, and was winning victory after victory over the im- 
perial troops. Magdeburg had entered into an alliance with 
the Swedish King, by which he was granted free passage 
through the city, while, on the other hand, he promised pro- 
tection to the city. 

The imperial army under Tilly and Pappenheim laid siege 
to the city. On the one side there was hope that Gustavus 
would arrive in time to effect a rescue; on the other, a de- 
termination to conquer before such aid could arrive. While 
Gustavus was on his way to the rescue, Magdeburg was 
taken by stonn, and the most horrible scene of the Thirty 
Years' War was enacted. Tilly gave up the city to plunder, 
and his soldiers without merc3" killed men, women, and 
childre.n. In the midst of the scene of carnage the city was 
set on fire, and soon the horrors of fire were added to the 

20 



THE AGE OF GALILEO 



horrors of the sword. In less than twelve hours twenty 
thousand people perished. 

Guericke's house and family were saved, but the suffer- 
ings of the city were not yet ended. In five years the enemy 
was again before the walls, and Magdeburg, then in the 
possession of the Swedes, was compelled to yield to the 
combined Saxon and imperial troops. Guericke entered the 
service of Saxony, and was again made mayor of the city. 

In the midst of these scenes of war, he found time to con- 
tinue his studies. He made the first air-pump, and with it 
performed experiments which led to some very important 
results. 

The experiments which Guericke made with his air-pump 
aroused the attention of the princes, and especially Emperor 
Ferdinand. Guericke was called to perform his experi- 
ments before the Emperor. The most striking of these 
experiments he performed with two hollow copper hemi- 
spheres about a foot in diameter, fitted closely together. 
When the air was pumped out, sixteen horses were barely 
able to pull the hemispheres apart, though, when air was 
admitted, they fell apart of their own weight. 

Another experiment which astonished his audience was 
performed with the cylinder of a large pump (Fig. 5). A 
rope was tied to the piston. This rope was passed over a 
pulley, and a large number of men applied their strength 
to the rope to hold the piston in place. When the air was 
taken out of the cylinder, the piston was forced down by 
air-pressure, and the men were lifted violently from the 
ground. This experiment, as we shall see, was of great im- 
portance in the invention of the steam-engine. 

21 




FIG. 5 — guericke's air-pump 
Men lifted from the ground by air-pressure. 



THE AGE OF GALILEO 



Guericke's study of air-pressure led him to make a water 
barometer (Fig. 6). This consisted of a glass tube about 
thirty feet long dipping into a dish of water. The tube was 
filled with water, and the top projected above the roof of 
the house. On the water in the tube he placed a wooden 
image of a man. In fair weather the image would be seen 
above the housetop. On the approach of a storm the 
image would drop out of sight. This led his superstitious 
neighbors to accuse him of being in league with Satan. 

The first electrical machine w^as made by Guericke. This 
was simply a globe of sulphur turning on a wooden axle. 
He observed that when the dry hand was held against the 
revolving globe, the globe would attract bits of paper and 
other light objects. 

Robert Boyle and the Presstire of Air and Steam 

Robert Boyle, in England, improved the air-pump and 
performed many new and interesting experiments with it. 
One of his experiments was to make water boil by means 
of an air-pump without applying heat. It is now well 
known that water when boiling on a high mountain is not 
so hot as when boiling down in the valley. This is because 
the air-pressure is less on the mountain top than in the val- 
ley. By using an air-pump to remove the air-pressure, water 
may be made to boil when it is still quite cold to the hand. 

Boyle compared the action of air under pressure to a 
steel spring. The ''spring" of the air is evident to us in 
the pneumatic tire of the bicycle or automobile. Boyle 
found that the more air is compressed the greater is its 
pressure or ''spring," and that steam as it expands exerts 



iJ«%S|i^S^|j^^ii^§ps| 



FIG. 6 — guericke's water barometer 

In fair weather the image appeared above the housetop. When a 
storm was approaching the image dropped below the roof into the 
house, 



THE AGE OF GALILEO 



less and less pressure. This is important in the steam- 
engine. 

Pascal and the Hydraulic Press 

It was Blaise Pascal, a Frenchman, who proved beyond 
the possibility of a doubt that air-pressure supports the mer- 
cury in a barometer, and 
lifts the water in a pump 
(Fig. 7). He had two mer- 
cury barometers exactly 
alike set up at the foot of 
a mountain. The mercury 
stood at the same height in 
each. Then one barometer 
was left at the foot of the 
mountain, and the other 
was carried to the summit, 
about three thousand feet 
high. The mercury in the 
second barometer then stood 
more than three inches low- 
er than at first. As the 
barometer was carried down 
the mountain the mercury 
slowly rose until, at the 
foot, it stood at the same 
height as at first. The par- fig- 7— a lift-pump 

, , ji_ j.i.ir,. Air pressing down on the water in 

ty stopped about half-way ^^^ ^^j^ ^^^J^ ^^^ ^^^^^ ^^ ^.^^ .^ ^^^^ 

down the mountain, allow- pump. The air can do this only when 

ing the barometer to rest the plunger is at work removing air or 

^ water and reducing the pressure mside 

there for some time, and the pump. 

25 




THE STORY OF GREAT INVENTIONS 



observing it carefully. They found that the mercury stood 
about an inch and a half higher than at the foot of the moun- 
tain. During all this time the height of the mercury in the 
barometer which had been left at the foot of the mountain 
did not change. 

It is now known that when a barometer is carried up to 
a height of nine hundred feet, the mercury stands an inch 
lower than at the earth's surface. For every nine hundred 
feet of elevation the mercury is lowered about one inch. 
In this way the height of a mountain can be measured, and 
a man in a balloon or an air-ship can tell at what height he 
is sailing. For this purpose, however, a barometer is used 
that is more easily carried than a mercury barometer. 

Pascal invented the hy- 
draulic press, a machine 
with which he said he could 
multiply pressure to any 
extent, which reminds us 
of Archimedes' saying that, 
with his own hand, he could 
move the earth if only he 
had a place to stand. Pas- 
cal could so arrange his 
machine that a man press- 
ing with a force of a hun- 
dred pounds on the handle 
could produce a pressure of many tons. In fact, a man can 




lib 

m 



m 
I 



nmz^mmiis:^ 



'//////////////////// / / //// /// / ////// /// //////// , 



77/77 7///, 



FIG. 8 A SIMPLE HYDRAULIC PRESS 

A one - pound weight holds 
hundred pounds. 



up 



so arrange this machine that he can lift any weight what- 
ever (Fig. 8). 

The hydraulic press has two cylinders. One cylinder 

26 



THE AGE OF GALILEO 



must be larger than the other. The two cyHnders are filled 
with a liquid, as water or oil, and are connected by a tube 
so that the liquid can flow from one cylinder into the other. 
There is a tightly fitting piston in each cylinder. If one 
piston has an area of one square inch, and the other has an 
area of one hundred square inches, then every pound of 
pressure on the small piston causes a hundred pounds of 
pressure on the large piston. A hundred pounds on the 
small piston would lift a weight of ten thousand pounds on 
the large piston. But we can see that the large piston can- 
not move as fast as the small one does. Though we can 
lift a very heavy weight with this machine, we must ex- 
pect this heavy weight to move slowly. There must be a 
loss in speed to make up for the gain in the weight lifted 
(Fig. 9). An hydraulic press with belt - driven pump is 
illustrated in Fig. 10. 

Newton 

Sir Isaac Newton as a boy did not show any unusual 
talent. In school he was backward and inattentive for a 
number of years, until one day the boy above him in class 
gave him a kick in the stomach. This roused him and, to 
avenge the insult, he applied himself to study and quickly 
passed above his offending classmate. His strong spirit 
was aroused, and he soon took up his position at the head 
of his class. 

It was his delight to invent amusements for his class- 
mates. He made paper kites, and carefully thought out 
the best shape for a kite and the number of points to which 
to attach the string. He would attach paper lanterns tg 

27 



THE STORY OF GREAT INVENTIONS 




FIG. 9 HOW AN HYDRAULIC PRESS WORKS 

One man with the machine can exert as much pressure as a hundred 
men could without the machine. The arrows show the direction in 
which the liquid is forced by the action of the plunger p. The large 
piston P is forced up, thus compressing the paper. 

these kites and fly them on dark nights, to the deHght of 
his companions and the dismay of the superstitious country 
people, who mistook them for comets portending some great 
calamity. He made a toy mill to be run by a mouse, which 
he called the miller; a mechanical carriage, run by a handle 

2§ 



THE AGE OF GALILEO 



worked by the person inside, a water-clock, the hand of 
which was turned by a piece of wood which fell or rose by 
the action of dropping water. 

At the age of fifteen, his mother, then a widow, removed 
him from school to take charge of the family estate. But 
the farm was not to his liking. The sheep went astray, 




FIG. 10 AN HYDRAULIC PRESS WITH BELT-DRIVEN 

PUMP 

29 



THE STORY OF GREAT INVENTIONS 

and the cattle trod down the corn while he was perusing 
a book or working with some machine of his own con- 
struction. His mother wisely permitted him to return to 
school. After completing the course in the village school 
he entered Trinity College, Cambridge. 

Gravitation 

It was in the year following his graduation from Cam- 
bridge that he made his greatest discovery — that of the law 
of gravitation. A plague had broken out in Cambridge, 
to escape which Newton had retired to his estate at Wools- 
thorpe. Here he was sitting one day alone in the garden 
thinking of the wonderful power which causes all bodies to 
fall toward the earth. The same power, he thought, which 
causes an apple to fall to the ground causes bodies to fall 
on the tops of the highest mountains and in the deepest 
mines. May it not extend farther than the tops of the 
mountains? May it not extend even as far as the moon? 
And, if it does, is not this power alone able to hold the 
moon in its orbit, as it bends into a curve a stone thrown 
from the hand? 

There followed a long calculation requiring years to com- 
plete. Seeing that the results were likely to prove his 
theory of gravitation, he was so overcome that he could 
not finish the work. When this was done by one of his 
friends, it was found that Newton's thought was correct — 
that the force of gravitation which causes bodies to fall at 
the earth's surface is the same as the force which holds the 
moon in its orbit. As the earth and moon attract each 

30 



THE AGE OF GALILEO 



other, so every star and planet attracts every other star 
and planet, and this attraction is gravitation. 

Colors in Stinlight 

About the same time that he made his first discoveries 
regarding gravitation, he took up the study of light with a 
view to improving the construction of telescopes. His first 
experiment was to admit sunlight into a darkened room 
through a circular hole in the shutter, and allow this beam 
of light to pass through a glass prism to a white screen be- 
yond. He expected to see a round spot of light, but to 
his surprise the light was drawn out into a band of brilliant 
colors. 

He found that the light which comes from the sun is not 
a simple thing, but is composed of colors, and these colors 
were separated by the glass prism. In the same way the 
colors of sunlight are separated by raindrops to form a rain- 
bow. The colors may be again mingled together by passing 
them through a second prism. They will then form a white 
light. 

Suppose that the light of the sun were not composed of 
different colors, that all parts of white light were alike, 
then there would be no colors in nature. All the trees and 
flowers would have a dull, leaden hue, and the human 
countenance would have the appearance of a pencil-sketch 
or a photographic picture. The rainbow itself would 
dwindle into a narrow arch of white light; the sun would 
shine through a gray sky, and the beauty of the setting 
sun would be replaced by the gray of twilight (Fig. ii). 
3 31 



THE STORY OF GREAT INVENTIONS 




FIG. II NEWTON S EXPERIMENT WITH THE PRISM 

Sunlight separated into the colors of the rainbow. The seven colors 
are: violet, indigo, blue, green, yellow, orange, red. 

One of Newton's inventions was a reflecting telescope — 
that is, a telescope in which a curved mirror was used in 
place of a lens. He made such a telescope only six inches 
long, which would magnify forty times. 

Newton was a member of the Convention Parliament, 
which declared James II. to be no longer King of England 
and tendered the crown to William and Mary. He was 
made a knight by Queen Anne in 1705. 

His knowledge of chemistry was used in the service of 
his country when he was Master of the Mint. It was his 
duty to superintend the recoining of the money of England, 
which had been debased by dishonest officials at the mint. 
He did his work without fear or favor. 

Once a bribe of £6000 ($30,000) was offered him. He 

32 



THE AGE OF GALILEO 



refused it, whereupon the agent who made the offer said to 
him that it came from a great duchess. Newton repHed: 
" Tell the lady that if she were here herself, and had made 
me this offer, I would have' desired her to go out of my 
house; and so I desire you, or you shall be turned out." 

Although Newton's discoveries in the world of thought 
were among the greatest ever made by man, he regarded 
them as insignificant compared with the truth yet undis- 
covered. He said of himself : " I do not know what I may 
appear to the world, but to myself I seem to have been 
only like a boy playing on the sea-shore and diverting 
myself in now and then finding a smoother pebble or a 
prettier shell than the ordinary, whilst the great ocean of 
truth lay all undiscovered before me." 



Chapter III 

THE EIGHTEENTH CENTURY 

James "Watt and the Steam-Engfne 

IF you had visited the coal-mines of England and Scot- 
land three hundred years ago, you might have seen 
women bending under baskets of coal toiling up spiral 
stairways leading from the depths of the mines. At some 
of the mines horses were used. A combination of windlass 
and pulleys made it possible for a horse to lift a heavy 
bucket of coal. There came a time, however, when slow 
and crude methods such as these could not supply the coal 
as fast as it was needed. The shallower mines were being 
exhausted. The mines must be dug deeper. The demand 
for coal was increasing. The supply of coal, it was thought, 
would not last until the end of the century. The wood 
supply was already exhausted. It seemed that England 
was facing a fuel famine. 

There was only one way out of the difficulty. A machine 
must be invented that would do the work of the women 
and horses, a machine strong enough to raise coal with 
speed from the deepest mines. Then it happened that two 
great inventors, Newcomen and Watt, arose to produce the 
machine that was needed. When the world needs an in- 

34 



THE EIGHTEENTH CENTURY 

vent ion it seldom fails to appear. It is true of the world, 
as of an individual, that ''Necessity is the mother of in- 
vention." 

In the mean time Torricelli had performed his famous 
barometer experiment, and Otto von Guericke had aston- 
ished princes with proofs of the pressure of the air. There 
was no apparent connection between these experiments 
and the art of coal-mining, yet these discoveries made pos- 
sible the steam-engine which was to revolutionize first the 
coal-mining industry and, later, the entire industrial world. 

The First Steam-Engine with a Piston 

The first steam-engine with a piston was made by Denys 
Papin, a Frenchman. Pap in had observed that, in Guer- 
icke 's experiment, air-pressure lifted several men off their 
feet. So he thought the air could be made to lift heavy 
weights and do useful work. But how should he produce 
the vacuum ? His first thought was to explode gunpowder 
beneath the piston. The gunpowder engine had been tried 
by others and found wanting. He next turned his atten- 
tion to steam, and discovered that if the piston were forced 
up by steam and then the steam condensed, a vacuum was 
formed beneath the piston, and air-pressure forced the pis- 
ton to descend. If the piston were attached to a weight 
by a rope passing over a pulley, then, as the piston de- 
scended, it would lift the weight. Papin' s engine consisted 
simply of a cylinder and piston (Fig. 12). There was no 
boiler, but the water was placed in the cylinder beneath 
the piston. A fire was placed under the cylinder and, as 

35 



THE STORY OF GREAT INVENTIONS 



the water boiled, the steam raised the piston. Then the 

fire was removed and, as the cyHnder cooled, the steam 

condensed, and the piston was forced down by air-pressure. 

- This was a slow and awk- 




ward method. The engine 
required several minutes to 
make one stroke. 

The principle of Papin's 
engine was first success- 
fully applied by Thomas 
Newcomen. Newcomenwas 
a blacksmith by trade,. and 
his great successor, Watt, 
was a mechanic. Thus we 
see that great discoveries 
soon become common prop- 
erty. The blacksmith and 
the mechanic soon learn to 
use the discoveries of the 
scientist. 

Newcomen's Engine 



FIG. 12 — papin's engine Jn thc Ncwcomcn engine 

The first steam-engine with a piston. ^^^ piston mOVed a Walk- 
When the piston B was forced down 

by air-pressure, a weight was Hfted ing-beam tO whlch WaS at- 
by means of a rope TT passing over tached a pump-rod. Steam 
^ ' was used merely to bal- 

ance the air-pressure on the piston and allow the pump- 
rod to descend by its own weight. The steam was con- 

36 




THE EIGHTEENTH CENTURY 

densed in the cylinder, and the pressure of the air forced 
the piston down. Thus the work of raising water in 
the pump was done by the air. Newcomen's first engine 
made twelve strokes a minute, and at each stroke lifted 
fifty gallons of water fifty yards. He used this engine in 
pumping water from the mines, and also made engines for 
lifting coal. 

At first the steam was condensed by throwing cold water 
on the outside of the cylinder. But one day the engine 
suddenly increased its speed and continued to work with 
unusual rapidity. The upper side of the piston was cov- 
ered with water to make the piston air-tight, and it was 
found that this water was entering the cylinder through 
a hole that had worn in the piston, and this jet of cold 
water was rapidly condensing the steam. This was the 
origin of "jet condensation." 

After this steam and water were alternately admitted to 
the cylinder through cocks turned by hand. A boy, Hum- 
phrey Potter, to whom this work was intrusted, won fame 
by tying strings to the cocks in such a way that the engine 
would turn the cocks itself and the boy, Humphrey, was 
free to play. This device was the origin of valve-gear.^ 

Newcomen's engine was extensively used. The tin and 
copper mines of Cornwall were deepened. Coal-mines were 
sunk to twice the depth that had been possible. But as 

^ Any device by which a steam-engine operates the valves which admit 
steam to the cylinder is called ' ' valve-gear. ' ' One form of valve-gear is 
the link motion invented by Stephenson. This form will be described 
in connection with the locomotive. A simple valve-rod, worked by an 
eccentric such as is used on most stationary engines, is also a form of valve- 
gear. 

37 



THE STORY OF GREAT INVENTIONS 

the mines were deepened the cost of running the engines 
increased. The largest engines consumed about $15,000 
worth of coal per year. The Newcomen engine required 
about twenty-eight pounds of coal per hour per horse-power, 
while a modern engine consumes less than two pounds. 
Again, because of increased cost, mines were being aban- 
doned. Such was the situation when James Watt came 
into the field of action. 

Watt had learned the mechanic's trade in one year in a 
London shop, and, because he had not passed through an 
apprenticeship of seven years, the Guild of Hammermen, a 
labor- union of his time, refused him admission, and this 
refusal meant no employment. He found shelter, however, 
in the University of Glasgow, and Was there provided with 
a small workshop where he could make instruments for 
sale. 

Wattes Engine 

A small Newcomen engine belonging to the University of 
Glasgow was out of repair. London mechanics had failed 
to make it work. The job was given to Watt. That he 
might do a perfect piece of work on this engine, he made 
a study of all that was then known relating to steam 
(Fig. 13). 

He saw that there was a great loss of heat in admitting 
cold water into the cylinder to condense the steam, and 
that, to prevent this loss, the cylinder must be kept always 
as hot as the steam that enters it. While thinking tapon 
this problem the idea came to him that, if connection were 
made between the cylinder and a tank from which the air 

38 




FlG. 13 THE NEWCOMEN ENGINE, IN REPAIRING WHICH 

WATT WAS LED TO HIS GREAT DISCOVERIES 

Preserved in the University of Glasgow. 



THE STORY OF GREAT INVENTIONS 

had been pumped out, the steam would rush into the tank, 
and might there be condensed without cooHng the cyHnder. 
This was the origin of the condenser. 

We have seen that, in the Newcomen engine, the steam 
acted only on the under side of the piston, air acting on 
the upper side. It occurred to Watt that the steam should 
act on both sides of the piston. So he proposed to put an 
air-tight cover on the cylinder with a hole and stuffing-box 
for the piston to slide through and to admit steam to act 
upon it instead of air. Thus he was led to invent the double- 
acting engine. The action in the cylinder of Watt's engine 
was the same as that of the modern engine. 

To save the power of steam, Watt arranged the valve in 
his engine in such a way that the steam was cut off from 
the cylinder when the piston had made about one-fourth 
of a stroke. The steam in the cylinder continues to ex- 
pand and drive the piston. This device more than doubles 
the amount of work that the steam will do (Fig. 14). 

Horse-Power of an Engine 

When horses were about to be replaced by the steam- 
engine at the mines, the question was asked: **How many 
horses will the engine replace ?" Tests were made by Watt 
and others before him of the rate at which a horse could 
work in pumping water or in lifting a weight by means of 
a pulley. Watt's experiments showed that "a good Lon- 
don horse could go on lifting 150 pounds over a pulley at 
the rate of 2| miles an hour or 220 feet per minute, and 
continue the work eight hours a day." This would be 

40 



THE EIGHTEENTH CENTURY 

equal to lifting 33,000 pounds one foot high every minute. 
This rate of doing work he called a horse-power. It is more 
than the average horse can do, but this number was used by 
Watt that he might give good measure in his engines. The 
horse-power of an engine at that time meant the rate of 



SLIDE VALVE 




FIG. 14 CYLINDER OF WATT S STEAM-ENGINE 

Arrows show the course of the steam. 



work in lifting water or coal. Now it means the rate of 
work done by the steam upon the piston, so that to find 
the useful horse-power of an engine we must deduct the 
work wasted in friction. 

The indicator for measuring the pressure of steam in the 
cylinder and the fiy-ball governor are also inventions made 

41 



THE STORY OF GREAT INVENTIONS 

by Watt (Fig. 15) . The fly -ball governor replaced the throt- 
tle-valve which was at first used by Watt to regulate the speed 
of his engines. The throttle- valve is still used on locomotives. 
At the end of the eighteenth century the steam-engine 
was full grown. It remained for the nineteenth century to 
apply the engine to locomotion on sea and land, to develop 
the steam-turbine, and so to increase the power of the 




PIG. 15 A FLY-BALL GOVERNOR 

The balls as they rotate regulate the admission of steam 
to the cylinder by means of the lever L and the rod R. 

steam-engine that, early in the twentieth century, a 68,000- 
horse-power engine should speed an ocean liner across the 
Atlantic in five days. 

42 



THE EIGHTEENTH CENTURY 



The Lcyden Jar 

The first electrical invention of practical use was made 
by Benjamin Franklin. In Franklin's time great interest 
in electricity had been aroused by the strange discovery 
of a German professor, Pieter van Musschenbroek, of the 
University of Leyden. This professor had tried what he 
called a new but terrible experiment. He had suspended 
by two silk threads a gun-barrel which received electricity 
from an electrical machine. From one end of the gun-barrel 
hung a brass wire. The 
lower end of this wire dip- 
ped in a jar of water. He 
held the jar in one hand, 
while with the other he 
tried to draw sparks from 
the gun -barrel. Suddenly 
he received a shock which 
seemed to him like a light- 
ning stroke. So violent was 
the shock that he thought 
for a moment it would end 
his life. 

Out of this experiment came the Leyden jar, which for a 
century and a half was of no practical use, but which now 
forms an important part of every wireless telegraph equip- 
ment. The Leyden jar is simply a glass bottle or jar coated 
with tin-foil both inside and outside (Fig. i6). When 
charged with electricity the jar will hold its charge until 
the two coatings are connected by a metal wire or other 

43 




FIG. l6 A LEYDEN JAR 



THE STORY OF GREAT INVENTIONS 

good conductor of electricity. A person may receive a strong 
shock by holding the jar in one hand and touching a knob 
connected to the inner coating with the other hand. 

Popular interest in electricity was aroused by this dis- 
covery. The friction electrical machine and the Ley den 
jar were simple and easy to make. People of fashion found 
them interesting and amusing, the more so because of the 
shock felt on taking through the body the discharge from 
the "wonderful bottle," and the fact that several persons 
could receive the shock at the same instant. On one 
occasion the Abbe Nollet discharged a Ley den jar through 
a line composed of all the monks of the Carthusian Monastery 
in Paris. As the line of serious-faced monks a mile in length 
jumped into the air, the effect was ridiculous in the extreme. 

Conductors and Insulators 

About this time other great electrical discoveries were 
made. Early in the century, Stephen Gray discovered 
that some objects conduct electricity and others do not. 
He discovered that, when a glass tube is electrified by 
rubbing, it will attract and repel light objects. In the same 
way a comb or penholder of rubber may be electrified 
by rubbing it on the sleeve. A bit of paper which touches, 
the comb becomes electrified. Electricity can be trans- 
ferred from one object to another. Gray discovered further 
that contact is not necessary, that a hempen thread or a 
wire will carry an electric charge from one object to an- 
other. A silk thread will not carry the electric charge. 
"Some things convey electricity," he said, "and some do 

44 



THE EIGHTEENTH CENTURY 

not, and those which do not can be used to prevent the 
electricity escaping from those which do." Could this ob- 
scure inventor have seen a modem telegraph line with the 
glass insulators on the poles, which prevent the electric 
current escaping from the telegraph wire, he might have 
realized the importance of his discovery. He set up a line 
of hempen thread six hundred and fifty feet long, and with 
an electrical machine at one end of the line electrified a 
boy suspended from the other end. 

Two Kinds of Electric Charge 

A Frenchman, DuFay, while carrying further the experi- 
ments of Gray, was watching a bit of gold-leaf floating in the 
air. The gold-leaf had been repelled after contact with 
his electrified glass tube. Thinking to try the action of 
two electrified objects on the gold leaf, he rubbed a piece of 
gum-copal and brought it near the leaf. To his astonish- 
ment the leaf, which was repelled by the glass tube, was 
attracted by the gum-copal. He repeated the experiment 
again and again, and each time the leaf was repelied by the 
glass and attracted by the gum. He concluded from this 
that there are two kinds of electricity, which he named 
"vitreous" and "resinous." The two kinds of electric 
charge were called by Franklin "positive" and "negative." 

Franklin made a battery of Leyden jars, connecting the 
inner coating of one to the outer coating of the next through- 
out the series. In this way he could get a much stronger 
spark than with a single jar. On one occasion he nearly lost 
his life by taking a shock from his battery of Leyden jars. 

45 



THE STORY OF GREAT INVENTIONS 

He magnetized and demagnetized steel needles by passing 
the discharge from his Leyden jars through the needles. 



Franklin's Kite Experiment 

The conjecture that lightning is of the same nature as the 
spark from the Leyden jar or the electrical machine had 
gained a hold on the minds of others before Franklin. In 
France sparks had been drawn from a rod ninety-nine feet 
high, but this did not reach into the clouds. Franklin de- 
termined to send a kite into a thunder-cloud, thinking elec- 
tricity from the cloud would follow the string of the kite 
and could be stored in a Leyden jar, and used like the charge 
from an electrical machine. He had felt the power of a 
Ley den- jar discharge, and through it had nearly lost his 
life. He knew that lightning is far more powerful than any 
battery of Leyden jars, and yet to test the truth of his 
theory, that lightning is an electrical discharge, he was 
about to draw the lightning to his hand. He knew little of 
conductors of electricity. Whether the cord would draw 
little or much of the ''electric fire" he knew not. So far as 
he knew he was toying with death. 

The kite was made of two light strips of cedar placed 
crosswise, and a large silk handkerchief fastened to the 
strips. A sharp wire about a foot long was fastened to 
one of the strips. To the lower end of the cord he attached 
a key and a silk ribbon. By means of the ribbon he held 
the cord to insulate it from his hand. The kite soared into 
the clouds, and Franklin and his son stood under a shed 
awaiting the coming of the "electric fire "(Fig. 17). Soon 

46 




FIG. 17 ^FRANKLIN S KITE EXPERIMENT 

Taking electriHty from the clouds. 



THE STORY OF GREAT INVENTIONS 

the fibres of the cord began to bristle up. He approached 
his knuckles to the key. A spark passed. He brought up 
a : Ley den jar and charged it with electricity from the 
cloud, and found that with this charge he could do every- 
thing that could be done with electricity from his machine. 
He had proved the identity of lightning and electricity. 

The Lightning-Rod 

Some time before, he had discovered the action of a 
point in discharging electricity. He said: "If you fix a 
needle to the end of a gun-barrel like a little bayonet, while it 
remains there the gun-barrel cannot be electrified so as to 
give a spark, for the electric fire continually runs out silently 
at the point." In the dark you may see a light gather upon 
the point like that of a firefly or glow-worm. If the needle 
is held in the hand and brought near to an object charged 
with electricity, the object is quietly discharged, and a 
light may be seen at the point of the needle. This action 
of points explains the light sometimes seen on the tops of 
ships' masts, called by sailors "Saint Elmo's fire," and 
perhaps, also, the observation of Caesar that, in a certain 
African war, the spears of the Fifth Roman Legion appeared 
tipped with fire. 

The lightning-rod was the outcome of Franklin's observa- 
tions, and this was the first practical invention relating to 
electricity. A building may be electrified by an electrified 
cloud passing over it. If the building is protected by 
pointed rods, the electric charge will quietly escape from 
the points. The lower ends of the rods must be in the 

48 



THE EIGHTEENTH CENTURY 

moist earth below the surface. The Hghtning-rod has not 
proved so great a protection as FrankHn supposed it would. 
He supposed that a lightning- stroke is a discharge in one 
direction only; but we now know that it is a rapid surging 
back and forth, and this fact accounts for the failure of the 
lightning-rods to furnish perfect protection. In surging 
back and forth, the lightning may skip from the lightning- 
rod to some metal object within the building, as a stove or 
radiator. The lightning-rod robbed the thunder-storm of 
its terrors to the timid, and in time dispelled the supersti- 
tion of people who believed that thunder and lightning are 
evidence of the wrath of the Deity. 

Franklin was the first to propose an answer to the ques- 
tion: What is electricity? He believed electricity to be a 
subtle fluid existing in all objects. If an object has more 
than a certain amount of this fluid, it is positively elec- 
trified; if less than this amount, it is negatively electrified. 

The ''one-fluid" theory of Franklin was soon met by the 
"two-fluid" theory proposed by Robert Symmer, for 
Franklin's theory had failed to explain why two bodies 
negatively electrified should repel each other. According 
to Symmer, an uncharged body contains an equal quantity 
of two different electrical fluids. An excess of one of these 
produces a positive charge, an excess of the other a negative 
charge. 

Symmer' s experiments are almost ludicrous. He wore 
two pairs of silk stockings, and found that white and black 
silk worn together became strongly electrified. When the 
two stockings worn on one foot were pulled off together, 
and then separated, they were found to be electrified, and 

49 



THE STORY OF GREAT INVENTIONS 

attracted each other so strongly that a force of about one 
pound was required to separate them. The two charges, 
negative and positive, could, however, be separated. He 
thought, therefore, that there are "two electrical powers," 
not one, as Franklin believed. His belief was strengthened 
by examining a quire of paper through which an electric 
spark had passed, and finding that "the edges of the holes 
were bent two different ways, as if the hole had been made 
in the quire by drawing two threads in contrary directions 
through it." 

There was a long controversy regarding the two theories, 
and neither quite gained possession of the field. Each con- 
tained some truth, and each had its weak points. The 
two had more in common than men at that time thought. 

Galvani and the Electric Ctirrent 

Franklin had proven that there is electricity in the atmos- 
phere, and that lightning is an electric discharge. A wide- 
spread interest in the electricity of the atmosphere followed 
this discovery. Aloisio Galvani, a physician in Bologna, 
Italy, in attempting to learn the effect of atmospheric elec- 
tricity on the nerves and muscles of the human body, made 
a discovery which led to the electric battery and a knowl- 
edge of electric currents. 

Having dissected a frog, he laid it on a table on which 
stood an electrical machine. When one of his assistants 
touched lightly the nerve of the thigh with the point of a 
knife while a spark was drawn from the electrical machine, 
the muscles contracted violently, as if they were attacked 

50 



THE EIGHTEENTH CENTURY 

by a cramp. When he held the knife by the bone handle, 
there was no convulsion as there was when he held it by 
the steel blade. 

He next thought it important to find out if lightning 
would excite contraction of the muscles. He stretched and 
insulated a long iron wire in the open air on the housetop 
and, as a storm drew near, hung on it a dissected frog. To 
the feet he fastened another long iron wire, which was al- 
lowed to dip in the water in the well. *'The result," he said, 
"came about as we wished. As often as the lightning broke 
forth, the muscles were thrown into repeated, violent con- 
vulsions, so that always, as the lightning lightened the sky, 
the muscle contractions and movements preceded the 
thunder and, as it were, announced its coming. It was 
best, however, when the lightning was strong, or the clouds 
from w^hich it broke forth were near the place of the experi- 
ment." 

He describes his greatest experiment as follows: "After 
we had investigated the power of atmospheric electricity in 
storms, our hearts burned with the desire to investigate 
the daily quiet electricity of the atmosphere. Therefore, as 
the prepared frogs, hung on an iron railing which surrounded 
a hanging garden on our house, with brass hooks inserted 
in the spinal cord, fell into convulsions not only when it 
lightened, but when the sky was calm and clear, I thought 
that the cause of these contractions was the changes in the 
electricity of the atmosphere. Then for hours, yes, even 
days, I observed the animals, but almost never a movement 
of the muscles could be seen. At last, tired with such fruit- 
less waiting, I began to press the brass hooks, which were 

SI 



THE EIGHTEENTH CENTURY 

fastened in the spinal cord, against the iron raiHng to see 
if such a trick would cause the muscles to contract, and if 
instead of changes in the atmospheric electricity any other 
changes would have any influence. I observed, indeed, 
vigorous contractions, but none which could be caused by 
the condition of the atmosphere." 

It was pressing the brass hook against the iron railing, 
thus forming an electric battery, that caused electricity to 
pass through the muscles of the frog. Galvani did not know 
that he had discovered a new source of electricity. He 
never arrived at a correct explanation of his results, and 
never knew the value of his discovery. 

Volta and the Electric Battery 

It was left for Alexander Volta to show that, in Galvani' s 
experiment, the muscles of the frog, together with the brass 
hook and the iron railing, formed an electric battery. Volta 
showed that an electric charge can be produced merely by 
bringing two different metals into contact. He found that, 
if he placed copper and zinc in sulphuric acid, or a solution 
of common salt, he could produce a continuous flow of 
electricity (Fig. i8). 

In the beginning of the year 1800 Volta made the first 
electric battery (Fig. 19). It was made of copper and 
zinc disks placed alternately, with a piece of wet cloth 
above each pair of disks. With his column of disks he 
could obtain a strong shock; indeed, many shocks, one 
after the other. This first battery of Volta's was a form 
of "dry battery." Later Volta devised his "crown of 

53 



THE STORY OF GREAT INVENTIONS 




FIG. 19 THE FIRST ELFXTRIC BATTERY 

No. I — A battery of one hundred pairs of copper and zinc disks. 
No. 2 — Two such batteries connected. 

By permission of the Italian Institute of Graphic Arts, Bergamo. 



cups," a form of wet battery similar to some batteries in 
use to-day. Each cup contained a strip of copper and a 
strip of zinc in dilute sulphuric acid. 

Volta did not know the real use of the liquid in his bat- 
tery, nor that the strength of the current depends on the 
rate at which the metal is dissolved by the acid; but he 
had discovered the electric current, and with this discovery 
began a new era in electrical invention. 



Chapter IV 

FARADAY AND THE FIRST DYNAMO 

MICHAEL FARADAY, a London newsboy, the son of 
a blacksmith, became the inventor of the dynamo, and 
prepared the way for the wonderful electrical inventions of 
the nineteenth century. He began his career as a book- 
binder's apprentice, employing his spare moments in read- 
ing the books he was binding. One of these books led him 
to make some simple experiments in chemistry. He also 
made an electrical machine, first with a glass bottle, and 
afterward with a glass cylinder. 

While an apprentice he wrote to his young friend, Ben- 
jamin Abbott: "I have lately made a few simple galvanic 
experiments, merely to illustrate to myself the first prin- 
ciples of the science. I was going to Knight's to obtain 
some nickel, and bethought me that they had malleable 
zinc. I inquired, and bought some — have you seen any 
yet ? The first portion I obtained was in the thinnest pieces 
possible. It was, they informed me, thin enough for the 
electric stick. I obtained it for the purpose of forming 
disks with which and copper to make a little battery. The 
first I completed contained the immense number of seven 
pairs of plates!!! and of the immense size of halfpence 

55 



THE STORY OF GREAT INVENTIONS 

each!!!!!! I, sir, I my own self, cut out seven disks of the 
size of half pennies each! I, sir, covered them with seven 
halfpence, and I interposed between them seven, or rather 
six, pieces of paper soaked in a solution of muriate of soda 
(common salt). But laugh no longer, dear A., rather 
wonder at the effects this trivial power produced." 

This tiny battery made of half pennies with zinc disks 
and salt solution would decompose a certain solution which 
Faraday tested. A larger battery made of copper and zinc 
disks with salt solution would decompose water from the 
cistern. When the wires from the larger battery were put 
in the cistern-water he saw a dense white cloud descending 
from the positive wire, and bubbles rising from the negative 
wire. This action continued until all the white substance 
was taken out of the water. 

Because of his interest in science, young Faraday attracted 
the attention of a Mr. Dance, a member of the Royal In- 
stitution and a customer of his master, Mr. Riebau. Through 
the kindness of Mr. Dance he heard four lectures by Sir 
Humphry Davy. He took notes on the lectures, wrote 
them out carefully, and added drawings of the apparatus. 
These notes he sent to Davy with a letter expressing 
the wish that he might secure employment at the Royal 
Institution. In a short time, after a warning from Sir 
Humphry that he had better stick to his business of book- 
binding, that "Science is a harsh mistress," his wish was 
granted, and we find him cleaning and caring for apparatus 
in the Royal Institution and assisting Davy in preparing 
for his lectures. 



56 



FARADAY AND THE FIRST DYNAMO 



Count Rumford 

Our story now takes us back to the time of the American 
Revolution. In America, we find a young man of nineteen, 
Benjamin Thompson by name, serving as major in the 
Second Regiment of New Hampshire. The appointment of 
so young a man as major, and his evident hold on the gov- 
ernor's favor, aroused the jealousy of the older officers. 
He was accused of being unfriendly to the cause of liberty. 
He denied the charge, and was acquitted by the committee 
of the people of Concord. A mob gathered round his house, 
but he escaped. Driven from his refuge in his mother's 
home, he fled to England, leaving his wife and child. Ap- 
pointed lieutenant-colonel in the British Army, he returned 
to America and fought against his former friends. 

The war having ended, he returned to England, thence 
to the Continent, intending to take part in an expected war 
between Austria and Turkey. A chance meeting with a 
Bavarian prince, Maximilian, changed the course of his life. 
This prince, while commanding on parade, saw Thompson 
among the spectators mounted on a fine English horse, 
and addressed him. Thompson informed him that he came 
from serving in the American war. The prince, pointing 
to a number of his officers, said: ''These gentlemen were in 
the same war, but against you. They belonged to the Royal 
Regiment of Deux Fonts, that acted in America under the 
orders of Count Rochambeau." Thompson dined with 
the prince and French officers. They conversed of war and 
the battles in which they met. The prince, attracted to the 

57 



THE STORY OF GREAT INVENTIONS 

colonel, induced him to pass through Munich, and gave him 
a letter to his uncle, the Elector of Bavaria. 

It was in Bavaria, the country to which such unexpected 
turns of fortune led him, that his greatest work was done. 
He entered the service of the Duke of Bavaria as aide-de- 
camp. It was his aim while in the service of the Bavarian 
Government to better the condition of the people. He in- 
troduced reforms in the army, used the soldiers to rid the 
country of beggars and robbers, and took steps to provide 
for the infirm and find employment for the strong, his 
motto being that people can best be made virtuous when 
first made happy. 

A Military Workhouse was opened for the beggars, and 
a House of Industry for the poor. A Military Academy 
was formed with a view to the free education of young peo- 
ple of talent for the public service. He became absorbed 
in the one aim of helping the poor. So thorough was his 
devotion to the people, and so deeply did he win their 
affection, that when he was dangerously ill a multitude of 
hundreds went in procession to the church to make public 
prayers for his recovery. 

He saw that tlie poor may be helped by teaching them 
to save, and in nothing is there greater need of saving than 
in fuel and heat. In the kitchens of the Military Academy 
and the House of Industry he carried out a series of experi- 
ments on the economy of fuel, and succeeded in greatly 
reducing the amount of fuel needed for cooking the food. 
He did this by using a "closed fireplace," the forerunner 
of the stove. The closed fireplace was in reality a brick 
stove, and was a great improvement over the open chimney 

58 



FARADAY AND THE FIRST DYNAMO 

fireplaces then in common use. He made the covers of 
the cooking utensils double, to save the heat, for he had 
found that heat cannot escape through confined air. 

Benjamin Thompson was knighted by George III., and 
in 1 791 he was made a Count of the Holy Roman Empire, 
and is known to the world of science as Count Rumford. 



Count Rumford's Experiment with the Cannon 

While in the service of the Duke of Bavaria, it became 
his duty to oi'ganize the field artillery. To provide cannon 
for this purpose, he erected a foundry and machine-shops. 
Being alert for any unusual fact relating to heat, he observed 
the very high temperature produced by the boring of the 
cannon. He was eager to learn how so much heat could 
be produced. For this purpose he took a cannon in the 
rough, as it came from the foundry, fixed it in the machine 
used for boring, and caused the cannon to be turned by 
horses while a blunt borer was forced against the end of the 
cannon. He first tested the temperature of the metal itself 
as it turned. Then he surrounded the end of the cannon 
with water in an oblong box fitted water-tight (Fig. 20). 

The cannon had been turning but a short time when he 
found by putting his hand in the water that heat had been 
produced. In two hours and thirty minutes the water 
actually boiled. Astonishment was expressed in the faces 
of the bystanders on seeing so large a quantity of water 
heated and actually made to boil without any fire. 

"Heat," Count Rumford said, "may thus be produced 
merely by the strength of a horse, and, in case of necessity, 

59 



FARADAY AND THE FIRST DYNAMO 

this heat might be used in cooking victuals. But no cir- 
cumstance can be imagined in which there is any advan- 
tage in this method of procuring heat, for more heat might 
be obtained by burning the fodder which the horse would 
eat." The meaning ot this last remark was not understood 
until the time of Robert Mayer, about fifty years later. 
Rumford had found that the work of a horse can produce 
heat, and heat, in a steam-engine, can do the work of a 
horse. Thus surely, though slowly, men were learning of 
the forces that move the world and do man's bidding. 

Count Rumford, true to his adopted land, returned to 
London and became the founder of the Royal Institution 
in which Faraday and his successors have achieved such 
marvellous results. He believed that the poor can be helped 
in no better way than by giving them knowledge, so that 
they can better their own condition. For this purpose 
he founded the Royal Institution. Here he intended that 
men skilled in discovery should gain new knowledge that 
would add to the comfort and happiness of the people. 

Davy 

In the English coal-fields many accidents due to the 
burning of fire-damp had occurred. Fire-damp is caused 
by gas issuing from the coal. On the approach of a flame 
this gas catches fire, and as it bums it produces a violent 
wind, driving the flame before it through the mine. Miners 
were scorched to death, suffocated, or buried under ruins 
from the roof. Hundreds of miners had been killed. No 
means of lighting the mines in safety had been devised. 

6i 



THE STORY OF GREAT INVENTIONS 

Sir Humphry Davy, Professor of Chemistry in the Royal 
Institution, was appealed to. After many experiments he 
devised a "safe lamp," which was a common miner's lamp 
enclosed in a wire gauze. This proved a perfect protection 
from fire-damp, and the Davy safety lamp has been used 
by miners the world over for more than a century. 

But Davy's best work was with the electric battery. 
Some of the facts most familiar to us were discovered by 
him. Volta had contended that the contact of the metals 
in a battery produces a current, that the liquid merely 
carries the electricity from one metal plate to the other. 
But Davy proved that there can be no current without 
chemical action. Whenever we put two metals in an acid 
or other solution that will dissolve one metal faster than 
the other, and connect the metals with a wire, an electric 
current is produced. If we use water with silver and gold, 
there is no current, because water will not dissolve either 
the silver or the gold. 

Davy discovered the metal, potassium, by means of his 
electric battery. Potassium is found in common potash 
and saltpetre, and, when separated, is a very soft metal. 
The newly discovered metal aroused great interest in other 
countries. When Napoleon heard of it, he inquired im- 
petuously how it happened the discovery had not been 
made in France. On being told that in France there had 
not been made an electric battery of sufficient power, he 
exclaimed: "Then let one be instantly made without re- 
gard to cost or labor." His command was obeyed, and he 
was called to witness the action of the new battery. Before 
any one could interfere he placed the ends of the wires 

62 



FARADAY AND THE FIRST DYNAMO 

under his tongue and received a shock that nearly deprived 
him of sensation. On recovering he left the laboratory 
without a word, and was never afterward heard to refer to 
the subject. 

Davy made many great discoveries, but the greatest was 
his discovery of Faraday. 

A journey on the Continent with Davy was an event in 
the life of Faraday, who up to that time had never to his 
own recollection travelled twelve miles from London. On 
this journey he met Volta, whom he describes as ''an hale 
elderly man, very free in conversation." He visited the 
Academy del Cimento, in Florence, and wrote: "Here was 
much to excite interest; in one place was Galileo's first 
telescope, that with which he discovered Jupiter's satellites. 
It was a simple tube of wood and paper, about three and a 
half feet long, with a lens at each end. There was also 
the first lens which Galileo made. It was set in a very 
pretty frame of brass, with an inscription in Latin 
on it." 

Faraday crossed the Alps and the Apennines, climbed 
Vesuvius, visited Rome, and saw a glow-worm. The last he 
thought as wonderful as the first. 

Shortly after his return to London he fell in love. Now, 
Faraday had determined that he would not be conquered 
by the master passion. In fact, he had written various 
aspersions on love, of which the following is a sample : 

" What is the pest and plague of human life ? 
And what the curse that .often brings a wife? 
'Tis Love. 
^ 63 



THE STORY OF GREAT INVENTIONS 

What is't directs the madman's hot intent, 
For which a dunce is fully competent? 
What's that the wise man always strives to shun, 
Though still it ever o'er the world has run? 
'Tis Love." 

But he reckoned not with his own heart. It is not long 
until we find him writing to Miss Sarah Barnard, a bright 
girl of twenty-one: "You have converted me from one 
erroneous way, let me hope you will attempt to correct 
what others are wrong. . . . Again and again I attempt to 
say what I feel, but I cannot. Let me, however, claim not 
to be the selfish being that wishes to bend your affections 
for his own sake only. In whatever way I can minister to 
your happiness, either by close attention or by absence, it 
shall be done. Do not injure me by withdrawing your 
friendship or punish me for aiming to be more than a friend 
by making me less." 

They were married and lived in rooms at the Royal 
Institution. No poet ever loved more tenderly than Fara- 
day. Truly, science does not dry up the heart's blood. 
At the age of seventy-one he wrote to his wife while absent 
from home for a few days: ** Remember me; I think as 
much of you as is good for either you or me. We cannot 
well do without each other. But we love with a strong 
hope of love continuing ever." 

Faraday's Electrical Discoveries 

Now we shall turn to Faraday's electrical discoveries 
and inventions. Men had long known that, in houses that 

64 



FARADAY AND THE FIRST DYNAMO 

have been struck by lightning, steel objects such as knives 
and needles are sometimes found to be magnetized. Ships 
struck by lightning had found their compass-needles point- 
ing south instead of north, or wandering in direction and 
worthless. Men had wondered how an electrical discharge 
could magnetize steel. They had tried the spark of the 
electrical machine with no definite result. Franklin, in his 
experiment of magnetizing a steel needle by passing an 
electric spark through it, could not tell before the spark was 
passed through the needle which end would be the north 
pole. There was no seeming connection between the di- 
rection of the electric discharge and the polarity of the 
needle. After the discovery of the electric battery, men 
tried to discover a relation between the electric current and 
magnetism. 

Oersted and Electromagnetism 

The first success in this direction was achieved by Hans 
Christian Oersted, a native of Denmark. Poverty impelled 
his father to take him from school at the age of twelve and 
place him in an apothecary's shop. The boy, Hans, foimd 
delight in the chemical work of the apothecary. His eager- 
ness to learn and the pressure of poverty led him to neglect 
the usual sports of boyhood and devote his leisure time to 
reading and study. Again he entered school, and, though 
paying his way by his own work, he graduated with honor 
from the University of Copenhagen. He was appointed 
Professor of Physics in this university, and here he made 
his first great discovery in electromagnetism. 

After working for seyeii years to discover a relation be- 
5 05 



THE STORY OF GREAT INVENTIONS 

tween current electricity and magnetism, he made a dis- 
covery which proved to be the first step in the invention of 
the dynamo. He was using a magnetic compass, which is 
a small magnetic needle balanced on a steel point. The 
needle points nearly north and south unless disturbed by 
a magnet brought near it. He had tried to find if a wire 
through which a current is flowing would disturb the com- 
pass as a magnet does. He had tried placing the wire east 
and west, thinking the compass-needle would follow the 




FIG. 21 OERSTED S EXPERIMENT 

An electric current flowing over the compass-needle toward the north 
causes the needle to turn until it points nearly west. 

By permission of Joseph G. Branch. 

wire as it does a magnet. One day, while lecturing to his 
students, it occurred to him for the first time to place the 
wire north and south over the compass-needle. He was 
surprised and perplexed as he did so to see the needle 
swing round and point nearly east and west (Fig. 21). On 
reversing the current the needle swung in the opposite 
direction. He had discovered the magnetic action of an 
electric current. It was learned soon afterward that a coil 
of wire with an electric current flowing through it acts like 

66 



FARADAY AND THE FIRST DYNAMO 



a magnet, and that a current flowing around a bar of soft 
iron makes the iron a magnet (Figs. 22 and 23). 





FIG 22. A COIL WITH A CURRENT 

FLOWING THROUGH IT ACTS 
LIKE A MAGNET 

The coil is picking up iron filings. 



FIG. 23 A BAR OF SOFT IRON WITH 

A CURRENT FLOWING AROUND 
IT BECOMES A MAGNET 



Ampere 

The news of Oersted's discovery aroused great interest 
throughout Europe. Soon aftei its announcement in France, 
Andre Marie Ampere made a discovery of equal importance. 
Oersted had discovered electromagnet ism. Ampere discov- 
ered electrical power or motion produced by an electrical 
current. 

The youth of Ampere was passed amid the stormy scenes 
of the French Revolution. His father had moved from his 

67 



THE STORY OF GREAT INVENTIONS 

country home to Lyons and become a justice of the peace. 
In the destruction of the city of Lyons during the Reign of 
Terror he lost his head under the guillotine. 

The blow was too great for Ampere, then a youth of 
eighteen. He had been a precocious child, advanced be- 
yond his years in all the studies of the schools. But now 
his strong mind failed. For a year he wandered about me- 
chanically piling up heaps of sand or gazing upon the sky. 
Then his mental power returned, and he took up with eager- 
ness the study of botany and poetry. 

He became a professor in the Polytechnic School in Paris, 
and it was while teaching in this school that he made his 
great discoveries. He found that two coils of wire can be 
made to attract or repel each other by an electric current. 
If the current flows through the two coils in the same direc- 
tion, they attract each other (Fig. 24) . If the current flows 





FIG. 24 TWO COILS WITH CUR- 
RENTS FLOWING IN SAME DIREC- 
TION ATTRACT EACH OTHER 



FIG. 25 TWO COILS WITH CUR- 
RENTS FLOWING IN OPPOSITE DI- 
RECTIONS REPEL EACH OTHER 



68 



FARADAY AND THE FIRST DYNAMO 

in opposite directions through the coils, they repel each 
other (Fig. 25). This is not very strange to us, for we 
know that a coil with a current flowing through it acts just 
like a magnet. Each coil then has a north pole and a south 
pole. If the coils are placed so that the two north poles or 
the two south poles are together, they will repel each other. 
If the north pole of one coil is near the south pole of the 
other, they will attract each other. 

Ampere believed that electric currents are flowing around 
within the earth, and that the earth has a north and a south 
magnetic pole for the same reason that a coil of wire has 
magnetic poles; that these poles are caused by the currents 
flowing around in the earth just as the poles of the coil are 
caused by the current flowing around in the coil. 

We do honor to the name of Ampere whenever we measure 
an electric current, for electric currents are measured in 
"amperes." 

Arago 

Another important discovery was made by a young 
Frenchman, Francois Arago, within a year of the time when 
Oersted and Ampere made their discoveries. The three 
great discoveries of these men were made in the years 18 19 
and 1820. The youth of Arago was full of adventure. He 
had assisted in making a survey in the Pyrenees, the haunt 
of daring robber-bands. Twice in his cabin he was visited 
by a chief of a robber-band who claimed to be a custom- 
house guard. On the second visit he said to the robber: 
"Your position is perfectly known to me. I know that you 
are not a custom-house guard. I have learned that you 

69 



THE STORY OF GREAT INVENTIONS 



are the chief of the robbers of the country. Tell me whether 
I have anything to fear from your confederates." The 
robber replied: **The idea of robbing you did occur to us; 
but, on the day that we molested an envoy from the French, 
they would direct against us several regiments of soldiers, 
and we are not so strong as they. Allow me to add that the 
gratitude which I owe you for the night's shelter is your 
surest guarantee." 

At a later time, when war between vSpain and France was 
threatened, he was accused of being a spy, and a mob was 

formed to put him out 
of the way. He escaped 
in disguise through the 
midst of the mob and 
boarded a Spanish ship. 
He was carried to Moroc- 
co, ran the gantlet of 
bloodthirsty Mussulmans 
in Algiers, escaped death 
by a hair's-breadth, and 
through it all clung to 
the papers which record- 
ed the results of the sur- 
vey in the mountains, 
and delivered them in 
safety to the ofhce of 
the Bureau of Longitude 
in Paris. 
Arago made a discovery which, with those of Oersted and 
Ampere, prepared the way for Faraday's great electrical 

70 




FIG. 26 ARAGO'S EXPERIMENT 

When the copper plate whirls the mag- 
net whirls also, though it does not touch 
the copper plate. 



FARADAY AND THE FIRST DYNAMO 



discoveries and the invention of the dynamo . He found that a 
plate of copper whirHng above or below a magnetic needle will 
draw the needle after it (Fig. 26) . He could make the speed of 
the whirling copper plate so great that the needle would whirl 
rapidly, following the 
copper plate. Faraday 
was the first to explain 
Arago's experiment. 

Faraday's First Electric 
Motor 

Faraday's first electri- 
cal discovery was made 
soon after that of Ara- 
go. Oersted had proven 
that an electric current 
acts on a magnet. The 
magnet turns at right 
angles to the wire. Far- 
aday saw that this is be- 
cause the north pole of 
the magnet tries to go 
round the wire in one 
direction, and the south 
pole tries to go round 
in the opposite direc- 
tion. He placed a magnet on end in a dish of mercury, 
with one pole of the magnet above the mercury, and found 
that the magnet would spin round a wire carrying a cur- 
rent. When the current acts on one pole of the magnet 

71 




FIG. 27 ONE POLE OP A MAGNET SPINS 

ROUND A WIRE THROUGH WHICH AN 
ELECTRIC CURRENT FLOWS 



THE STORY OF GREAT INVENTIONS 

only, the magnet spins round the wire (Fig. 27). So Fara- 
day's first electrical discovery prepared the way for the 
electric motor. 

An Electric Ctirrent Produced by a Magnet 

He had written in his note-book: "Convert magnetism 
into electricity." An electric current would magnetize iron. 
Would not a magnet produce an electric current ? This 
was his problem. 

He connected a coil of wire to an instrument that would 
tell when a current was flowing, and placed a magnet in the 
coil. Others had claimed, and Faraday at first believed, that 
a current would flow while the magnet lay quiet within the 
coil. But Faraday was alert for the unexpected, and the 
unexpected happened. For an instant, as he thrust the 
magnet into the coil, his instrument showed that a current 
was flowing. Again, as he drew the magnet quickly from 
the coil, a current flowed, but in the opposite direction 
(Fig. 28). From this simple experiment has grown the 
alternating-current machinery by which the power of 
Niagara is made to light cities and drive electric cars at a 
distance of many miles. 

A friend of Faraday, on learning of this discovery, wrote 
the following impromptu lines: 

"Around the magnet Faraday 
Was sure that Volta's lightnings play. 

But how to draw them from the wire? 
He took a lesson from the heart: 
'Tis when we meet, 'tis when we part, 
Breaks forth the electric fire." 
72 



FARADAY AND THE FIRST DYNAMO 





FIG. 28 WHEN A MAGNET IS THRUST INTO A COIL OF WIRE IT CAUSES A 

. CURRENT TO FLOW IN THE COIL, BUT THE CURRENT FLOWS 
ONLY WHILE THE MAGNET IS MOVING 
Drawing reproduced by permission of Joseph G. Branch. 

A magnet will produce an electric current in a wire, but 
only when the magnet or the wire is in motion. 



Detecting and Measuring an Electric Current 

The instrument which Faraday used to detect a current 
was derived from Oersted's experiment. When a current 
flows in a north-and- south direction over a compass-needle, 
the needle swings round. When the current stops flowing 

73 



THE STORY OF GREAT INVENTIONS 

the needle swings back to the north-and-south position. 
The effect on the needle is stronger if the current flows 
through a coil of wire and the coil is placed in a north-and- 
south position around the needle (Fig. 29). The stronger 
the current flowing through the coil the farther the needle 
will turn from the north-and-south position. 




FIG. 29 A COIL OF WIRE AROUND A COMPASS-NEEDLE 

The needle tells when a current is flowing, and how strong the current is. 

The coil and the needle together are called a galvanom- 
eter, and may be used to tell when a current is flowing, 
and also to indicate the strength of the current. 

An Electric Current Produced by the Magnetic Field of Another 

Current 

Faraday had found that a current flowing around a piece 
of iron will make the iron a magnet, and that a magnet in 
motion will cause a current to flow in a wire. It seemed 

74 



FARADAY AND THE FIRST DYNAMO 

to him that a second wire placed near the first should have 
a current produced in it without the presence of iron. He 
wound two coils of copper wire upon the same wooden spool. 
The wire of the two coils he separated with twine and calico. 
One coil was connected with a galvanometer, the other with 
a battery of ten cells, yet not the slightest turning of the 
needle could be observed. But he was not deterred by one 
failure. He raised his battery from ten cells to one hundred 
cells, but without avail. The current flowed calmly through 
the battery wire without producing, during its flow, any 
effect upon the galvanometer. During its flow was the 
time when an effect was expected. 

Again the unexpected happened. At the instant of mak- 
ing contact with the battery there was a slight movement 
of the needle. When the contact was broken, another slight 
movement, but in the opposite direction to the first (Fig. 
30). The current in one wire caused a current to flow 
in the other, but the current in the second wire con- 
tinued for an instant only at the making and breaking 
of the contact with the battery. This was the begin- 
ning of the induction-coil used to-day in wireless teleg- 
raphy. 

What was the secret of it ? Simply this : that a current 
in one wire will cause a current to flow in another wire near 
it, but only while the current in the first wire is changing. 
That is, at the instant when the first wire is connected to 
the battery, or its connection broken, a current is induced 
in the second wire. There is no battery or other source of 
current connected to the second wire; but a current flows 
in this wire because it is near a wire in which a current is 

75 



THE STORY OF GREAT INVENTIONS 

rapidly starting and stopping. When these two wires are 
wound in coils, together they form an induction-coil. The 
wire which we have called the first wire forms the ''primary" 




FIG. 30 FARADAY S INDUCTION-COIL 

Starting and stopping the battery current in the primary coil causes 
a changing magnetic field, and this causes a current to flow in the 
secondary coil. 

Drawing reproduced by permission of Joseph G. Branch. 

coil, and the one we have called the second wire forms the 
"secondary" coil. By repeatedly making and breaking the 
circuit in the primary coil we get an alternating current in 

76 



FARADAY AND THE FIRST DYNAMO 

the secondary coil. Fig. 31 is from a photograph of some 
of the coils actually used by Faraday. 



Faraday's Dynamo 

To invent a new electrical machine was Faraday's next 
aim. Arago's disk of copper whirling near a magnet had 
a current induced in it, so Faraday thought. It was the 




FIG. 31 HISTORICAL APPARATUS OF FARADAY IN THE ROYAL INSTITUTION 

Some of Faraday's transformer coils are shown here. The instrument 
on the left in a glass case is his galvanometer. 

action of this induced current which caused the magnet to 
follow the whirling disk. Could the current in Arago's disk 
be collected and caused to flow through a wire ? He placed 
a copper disk between the poles of a magnet. One galva- 

77 



THE STORY OF GREAT INVENTIONS 

nometer wire passed around the axis of the disk, the other he 
held in contact with the edge. He whirled the disk. The 
galvanometer needle moved. A current was flowing in the 
disk as it whirled. The current from the whirling disk 
flowed through the galvanometer. Faraday had discovered 
the dynamo (Fig. 32). 




FIG. 32 FARADAY S FIRST DYNAMO 

A current flows in the copper disk as it whirls between the poles 
of the magnet. 

By permission of Joseph G. Branch. 

78 



FARADAY AND THE FIRST DYNAMO 

All this work occupied but ten days in the autumn of 
183 1, though years of preparation had gone before. In 
these ten days the foundation was laid for the induction- 




FIG. ^^ FARADAY S LABORATORY, WHERE THE FIRST DYNAMO WAS MADE 

From the water-color drawing by Miss Harriet Moore. 

coil, modern dynamo - electric machinery, and electric 
lighting. Fig. 33 shows the laboratory in which Faraday 
did this work. 

Faraday continued to explore the field opened up be- 
fore him. In one experiment two small pencils of charcoal 
lightly touching were connected to the ends of a secondary 
6 79 



THE STORY OF GREAT INVENTIONS 

coil. A spark passed between the charcoal points when 
the primary circuit was closed. This was the first trans- 
fonner producing a tiny electric light (Fig. 34). 

Faraday discovered the induction-coil, the dynamo, and 
the transformer, and he showed that, in each of these, it is 
magnetism which produces the electric current. He had 




5EC0NDARYJA 
COIL 



FIG. 34 THE FIRST TRANSFORMER 



discovered the secret when he obtained a current by thrust- 
ing a magnet into a coil of wire. The space about a magnet 
in which the magnet will attract iron he called the ''magnetic 
field" (Figs. 35 and 36). In every case of magnetism caus- 
ing an electric current to flow in a coil of wire, the coil is 
in a magnetic field, and the magnetic field is changing — that 

80 



FARADAY AND THE FIRST DYNAMO 




FIG. 3 5 THE MAGNETIC FIELD IS THE SPACE AROUND A MAGNET IN 

WHICH IT WILL ATTRACT IRON 

The iron filings over the magnet arrange themselves along the "lines 
of force." 

is, the magnetic field is made alternately stronger and weak- 
er, or the coil moves across the magnetic field. The point is 
that magnetism at rest will not produce an electric current. 
There must be a changing magnetic field or motion. In 
Faraday's dynamo a copper disk whirled between the poles 




FIG. 36 MAGNETIC FIELD OF A HORSESHOE MAGNET 

81 



THE STORY OF GREAT INVENTIONS 

of a magnet and the whirling of the disk in the magnetic 
field caused an electric current. In the modern dynamo it 
is the whirling of a coil of wire in a magnetic field that 
causes a current to flow. In the induction-coil it is the 
change in the magnetic field that causes a current to flow 
in the secondary coil. A coil of wire with an electric 
current flowing through it will attract iron like a magnet. 
The primary coil with a current from a battery flowing 
through it acts in all respects like a magnet; but as soon 
as the current ceases to flow the magnetic field disappears — 
the coil is no longer a magnet. When we make and break 
the connection between the primary coil and the battery, 
then, we repeatedly make and destroy the magnetic field, 
and this changing magnetic field causes a current to flow 
in the secondary coil. The induction-coil is one form of 
transformer. We shall see later how the dynamo and the 
transformer developed in the nineteenth century. 

When a boy, Faraday had passed the current from his 
little battery through a jar of cistern-water, and saw in the 
water a ''dense white cloud" descending from the positive 
wire, and bubbles arising from the negative wire. Some- 
thing was being taken out of the water by the electric cur- 
rent. When he tried the experiment later in his laboratory, 
he found that, whenever an electric current is passed through 
water, bubbles of two gases, oxygen and hydrogen, rise 
through the water. He found that if the current is made 
stronger the bubbles are formed faster. The water in time 
disappears, for it has been changed or ''decomposed" into 
the two gases. 

It was the current from a battery that would decompose 

82 



F ARADAY AND THE FIRST DYNAMO 

water. The electricity from the electrical machine would 
do other things that he had never seen a battery current 
do. *'Do the battery and the electrical machine produce 
different kinds of electricity, or is electricity one and the 
same in whatever way it is produced ?" This was the query 
that troubled him. The answer to this question had been 
so uncertain that the effect of the voltaic battery had been 
termed ''galvanism," while that of the friction machine 
retained the name "electricity." 

Faraday tried many experiments in searching for an 
answer to this question. He found that the electricity of 
the machine will produce the same effect as that of a bat- 
tery if the machine is compelled to discharge slowly. An 
electrical machine or a battery of Ley den jars can be made 
to give out an electric current, and this current will affect 
a magnetic needle in the same way that a battery current 
will. It will magnetize steel. If passed through water, it 
will decompose the water into the two gases oxygen and 
hydrogen. In short, a current from an electrical niachine 
or a Ley den jar will do everything that a current from an 
electric battery will do. Faraday caused the Leyden jar 
to give a current instead of a spark by connecting the two 
metal coatings with a wet string. On the other hand, the 
discharge from a powerful electric battery will produce a 
spark and affect the human nerves in the same way as the 
discharge from the electrical machine. The same effects 
may be obtained from one as from the other. 

In the discharge from the machine, a small quantity of 
electricity is discharged under high pressure, as water may 
be forced through a small opening by very high pressure. 

83 



THE STORY OF GREAT INVENTIONS 

The voltaic cell, on the other hand, furnishes a large quantity 
of electricity at low pressure, as a street may be flooded by 
a broken water-main though the pressure is low. In fact, 
the quantity of electricity required to decompose a grain 
of water is equal to that discharged in a stroke of lightning, 
while the action of a dilute acid on the one-hundredth part 
of an ounce of zinc in a battery yields electricity sufificient 
for a powerful thunder-storm. 

Many tests were made, and the result was a convincing 
proof that electricity is the same whatever its source, the 
different effects being due to difference in pressure and 
quantity. "But in no case," said Faraday, "not even in 
those of the electric eel and torpedo, is there a production 
of electric power without something being used up to sup- 
ply it." 

Faraday's professional work would have made him 
wealthy. In one year he made £1000 ($5000), and the 
amount would have increased had he sold his services at 
their market value. But then there would have been no 
Faraday the discoverer. The world would have had to 
wait, no one knows how long, for the laying of the founda- 
tions of electrical industries. He chose to give up wealth 
for the sake of discovery. He gave up professional work 
with the exception of scientific adviser to Trinity House, 
the body which has charge of Great Britain's lighthouse 
service. Nor did he carry his discoveries to the point of 
practical application. As soon as he discovered one prin- 
ciple, he set out in pursuit of others, leaving the practical 
application to the future. 

Faraday loved the beauty of nature. The sunset he 

84 



FARADAY AND THE FIRST DYNAMO 

called the scenery of heaven. He saw the beauty of elec- 
tricity, which he said lies not in its mystery, but in the 
fact that it is under law and within the control of the human 
intellect. 

A "Wonderful Law of Nature 

Not long after Faraday made his first dynamo, Robert 
Mayer, a physician from Germany, was making a voyage 
to the East Indies which proved to be a voyage of discovery. 
He had sailed as the ship's physician, and after some 
months an epidemic broke out among the ship's company. 
In his treatment he drew blood from the veins of the arms. 
He was startled to see bright-red blood issue from the veins. 
He might almost have believed that he had opened an artery 
by mistake. It was soon explained to him by a physician 
who had lived long in the tropics that the blood in the veins 
of the natives, and of foreigners as well, in the tropics is 
of nearly the same color as arterial blood. In colder 
climates the venous blood is much darker than the arte- 
rial. 

He reasoned upon this curious fact for some time, and 
came to the conclusion that the human body does not 
make heat out of nothing, but consumes fuel. The fuel is 
consumed in the blood, and there the heat is produced. In 
the tropics less heat is needed, less fuel is consumed, and 
therefore there is less change in the color of the blood. 

When a man works he uses up fuel. If a blacksmith 
heats a piece of iron by hammering, the heat given to the 
iron and the heat produced in his body are together equal 
to the heat of the fuel consumed in his blood. The work a 

85 



THE STORY OF GREAT INVENTIONS 

man does, as well as the heat of his body, comes from the 
burning of the fuel in his blood. 

What is true of a man is true of an engine. The work 
the engine does, as well as the heat it produces, comes from 
the heat of the fuel in the furnace. Mayer found that one 
hundred pounds of coal in a good working engine produces 
the same amount of heat as ninety-five pounds in an engine 
that is not working. In the working engine the heat of the 
five pounds of coal is used up in the work of running the 
engine, and therefore does not heat the engine. Heat that 
is used in running the engine is no longer heat, but work. 
So Mayer said the heat is not destroyed, but only changed 
into work. He said, further, that the work of running the 
engine may be changed again into heat. 

Mayer's theory was opposed by many scientific men of 
Europe. One great scientist said to him that if his theory 
were correct water could be warmed by shaking. He re- 
membered what the helmsman had remarked to him on 
the voyage to Java, that water beaten about by a storm is 
warmer than quiet sea- water; but he said nothing. He 
went to his laboratory, tried the experiment, and some 
weeks later returned, exclaiming: *'It is so! It is so!" 
He had warmed water simply by shaking it. 

These results mean that work or energy cannot be de- 
stroyed. Though it changes form in many ways, it is never 
destroyed. Neither can man create energy; he can only 
direct its changes as the engineer, by the motion of his 
finger in opening a valve, sets the locomotive in motion. He 
does not move the locomotive. He directs the energy al- 
ready in the steam. 

86 



FARADAY AND THE FIRST DYNAMO 

Since the time of Galileo, men had caught now and then 
a glimpse of this great law. Galileo had stated his law of 
machines; that, when a machine does work, a man or a 
horse or some other power does an equal amount of work 
upon the machine. Count Rumford had performed his ex- 
periment with the cannon, showing that heat is produced 
by the work of a horse. Davy had proved that, in the 
voltaic battery, something must be used up to produce the 
current — the mere contact of the metals is not sufficient. 
Faraday had said that in no case is there a production of 
electrical power without something being used up to supply 
it. Mayer stated clearly this law of energy when he said 
that energy cannot be created or destroyed, but only 
changed from one form to another. 

And yet inventors have not learned the meaning of this 
law. They continue trying to invent perpetual - motion 
machines — machines that will produce work from nothing. 
This is what a perpetual-motion machine would be if such 
a machine were possible. For a machine without friction is 
impossible, and friction means wasted work — work changed 
into heat. A machine to keep itself running and supply 
the work wasted in friction must produce work from noth- 
ing. The great law of nature is that you cannot get some- 
thing for nothing. Whether you get work, heat, electricity, 
or light, something must be used up to produce it. For 
whatever you get out of a machine you must give an equiva- 
lent. This law cannot be evaded, and from it there is no 
appeal. 



Chapter V 

GREAT INVENTIONS OF THE NINETEENTH CENTURY 

THE discoveries of Faraday prepared the way for the 
great inventions of the nineteenth century. By the 
middle of the century men knew how to control the won- 
derful power of electricity. They did not know what elec- 
tricity is, nor do we know to-day, though we have made 
some progress in that direction ; but to control it and make 
it furnish light, heat, and power was more important. 

Before the inventions of James Watt made it possible to 
use steam-power, factories were built near falling water, so 
that water-power could be used. But the steam-engine 
made it possible to build great factories wherever a supply 
of water for the boilers could be obtained. Cities were built 
around the factories. Cities already great became greater. 
With the growth of cities the need of a new means of pro- 
ducing light and power made itself felt. Electricity prom- 
ised to become the Hercules that should perform the tasks 
of the modern world. 

Discovery gave way to invention. During the second 
half of the nineteenth century many great inventions were 
made and industries were developed, while discoveries were 
few until near the close of the century. Within this period 



N INETEENTH-CENTURY INVENTIONS 

the great industries which characterize our modern civiHza- 
tion, and which arose out of the discoveries that science had 
made in the centuries preceding, attained a high degree of 
development. In this chapter we shall trace the applica- 
tions of some of the discoveries with which we have now 
become familiar. This will lead us into the field of electri- 
cal invention, for we are dealing now with the beginning 
of the world's electrical age. 

Electric Batteries 

From the time of Volta to the time of Faraday the only 
means of producing an electric current was the ' ' voltaic bat- 
tery," so called in honor of Volta. The voltaic cell is the 
simplest form of electric battery. In this cell the zinc and 
copper plates are placed in sulphuric acid diluted with 
w^ater. As the acid eats the zinc, hydrogen gas is formed. 
This gas collects in bubbles on the copper plate and weakens 
the current. The aim of inventors was to produce a steady 
current, to devise a battery in which no gas would collect 
on the copper plate. They saw the need of a battery that 
would give out a current of unchanging strength until the 
zinc or the acid was used up. 

The first real improvement in the battery was made by 
Professor Daniell, of King's College, London. In the Daniell 
cell the zinc plate is in dilute sulphuric acid, and the copper 
plate is in a solution of blue vitriol or copper sulphate. 
Professor Daniell separated the two liquids by placing one 
of them in a tube formed of the gullet of an ox. This tube 
dipped into the other liquid. The hydrogen gas, as it was 

89 



THE STORY OF GREAT INVENTIONS 

formed by the acid acting on the zinc, could go through 
the walls of the tube, but was stopped by the copper sul- 
phate, and copper was deposited on the copper plate. This 
copper deposit in no way interfered with the current, so 
that the current was not weakened until the zinc plate or 
one of the solutions was nearly consumed. A cup of porous 
earthenware is now used in Daniell cells to separate the 




FIG. 37 A DANIELL CELL 

liquids (Fig. 37). By placing crystals of blue vitriol in the 
battery jar, the solution of blue vitriol can be kept up to 
its full strength for a very long time. The zinc in time is 
consumed, and must be replaced. 

90 



NINETEENTH-CENTURY INVENTIONS 




FIG. 38 A GRAVITY CELL 



In the gravity cell (Fig. 38) 
the same materials are used 
as in the Daniell cell — cop- 
per in copper sulphate, and 
zinc in sulphuric acid ; but 
there is no porous cup. The 
solutions are kept separate 
by gravity, the heavy cop- 
per sulphate being at the 
bottom. The gravity cell has 
until recently been extensive- 
ly used in telegraphy, and 
continues in use in short-dis- 
tance telegraphy and in au- 
tomatic block signals. The 

gravity and Daniell cells are used for closed-circuit work — 
that is, for work in which the current is flowing almost con- 
stantly. 

The Dry Battery 

Another important improvement was the invention of 
the dry battery. You will remember that the first battery, 
the one invented by Volta, was a form of dry battery; but 
it was a very feeble battery compared with the dry bat- 
teries now in use, so that we may call the dry battery a 
new invention. The dry battery is falsely named. There 
can be no battery without a liquid. In the dry battery 
the zinc cup forming the outside of the cell is one of the 
plates of the cell (Fig. 39). The battery appears to be dry 
because the solution of sal ammoniac is absorbed by blot- 
ting-paper or other porous substance in contact with the 

91 



THE STORY OF GREAT INVENTIONS 



zinc. The inner plate is carbon, and this is surrounded by 
powdered carbon and manganese dioxide — the latter to 
remove the hydrogen gas which collects on the carbon 
plate. This gas weakens the current when the circuit has 
been closed for a short time, but is slowly removed when 
the circuit is broken. Thus the battery is said to "recover." 

The dry cell will give 



Cdrbon. 
F^oj'ous substance tYtth 



d 



^Z 



mc 



mdnganese 
dioxide. 



a strong current, but for 
a short time only. It 
recovers, however, if al- 
lowed to rest. It can 
be used, therefore, only 
in '* open -circuit " work 
— such as door-bell cir- 
cuits, and some forms of 
fire and burglar alarm. 
A door -bell circuit is 
open nearly all the time, 
the current flowing only 
while the button is being 
pressed. Some forms of 
wet battery work in the 
same way as the dry bat- 
tery, and are used like- 
wise for open - circuit 
work. In these batteries carbon and zinc plates in a so- 
lution of sal ammoniac are used, the same materials as in 
the dry battery. The only difference is that in the dry 
battery the solution is absorbed by some porous substance 
and the battery sealed so that it appears to be dry, 

92 



FIG. 39 — SHOWING WHAT IS IN A DRY 
BATTERY 



NINETEENTH-CENTURY INVENTIONS 

The Storage Battery 

One of the greatest improvements in electric batteries is 
the storage battery. A simple storage battery may be^ 
made by placing two strips of lead in sulphuric acid diluted 
with water and connecting the lead strips to a battery of 
Daniell cells or dry cells. In a short time one of the lead 
strips will be found covered with a red coating. The sur- 
face of this lead strip is no longer lead but an oxide of lead, 
somewhat like the rust that forms on iron. If the lead strips 
are now disconnected from the other battery and connected 
to an electric bell, the bell will ring. We have here two 
plates, one of lead and one of oxide of lead, in dilute sul- 
phuric acid. This forms a storage battery. 
, The first storage battery was made of two sheets of lead 
rolled together and kept apart by a strip of flannel. The 
lead strips thus separated were immersed in dilute sulphuric 
acid. A current from another battery was passed through 
this cell for a long time — first in one direction, then in the 
other. This roughened the surface of the lead plates, so 
that the battery would hold a greater charge. The battery 
was then charged by passing a current through it in one 
direction only for a considerable length of time. Feeble 
cells were used for charging. It took days, and sometimes 
weeks, to charge the first storage batteries. Then the stor- 
age battery would give out a strong current lasting for a 
few hours. It slowly accumulated energy while being 
charged, and then gave out this energy rapidly in the form 
of a strong^ electric current. For this reason the storage 
battery was called an ''accumulator." 

93 



THE STORY OF GREAT INVENTIONS 



While charging the storage cell there was formed on the 
negative plate a coating of soft lead, and on the positive 
plate a coating of dark-brown oxide of lead. It was found 

better to apply these coat- 
ings to the lead plates be- 
fore making up the battery. 
Later it was found that 
the battery would hold a 
still greater charge if the 
plates were made in the 
form of "grids" (Fig. 40), 
and the cavities filled with 
the active material — the 
negative with spongy lead, 
and the positive with dark- 
brown lead oxide. Some 
excellent commercial stor- 
age batteries are made from 
lead plates by the action of 
an electric current, very 
much as Plante made his 
batteries. Fig. 41 shows 
one of these plates. 

The storage battery does 
not store up electricity. It 
produces a current in exactly the same way as any other 
battery — ^by the action of the acid on the plates. When 
this action ceases it is no longer a battery, though it may 
be made one again by passing a current through it in the 
opposite direction from that which it gives out. In this 

94 




FIG. 40 A STORAGE BATTERY, SHOW- 
ING THE "grids" 



NINETEENTH-CENTURY INVENTIONS 



it differs from the voltaic battery, for when such a battery 
is run down it can be restored only by adding new solution 
or new plates. The storage battery is especially useful for 
"sparking" in gas or gasolene motors. 

Edison has invented a storage battery that will do as 
much work as a lead battery of twice its weight. Edison's 
battery is intended especially for use in electric automobiles. 
By reducing the weight 



of the battery which 
the machine must car- 
ry the weight of the 
truck may also be re- 
duced. In the Edison 
battery the positive 
plates are made of a 
grid of nickel - plated 
steel containing tubes 
filled with pure nickel. 
The negative plate con- 
sists of a nickel-plated 
steel grid containing an 
oxide of iron similar to 
common iron-rust. 

After working a num- 
ber of years on this bat- 
tery and making nine 
thousand experiments, 
Edison thought he had 
it perfected, and indeed 
it was a great improve- 
7 




FIG. 41 A STORAGE - BATTERY PLATE 

MADE FROM A SHEET OF LEAD 



95 



THE STORY OF GREAT INVENTIONS 

merit over the storage batteries that had been used — much 
Hghter and cheaper, and more successful in operation. Two 
hundred and fifty automobiles were equipped with it, and it 
proved superior to lead batteries for this purpose. But it was 
not to Edison's liking. He threw the machinery, worth thou- 
sands of dollars, on the scrap-heap, and worked on for six 
years. He had then produced a battery as much better 
than the first as the first was better than the lead battery, 
and he was content to have the new battery placed oh the 
market. 

The Dynamo 

For the purpose of lighting and power the electric bat- 
tery proved too costly. Davy produced an arc light with 
a battery of four thousand cells. The arc was about four 
inches in length and yielded a brilliant light, but as the 
cost was six dollars a minute it was not thought practical. 
Attempts were made early in the century to use a battery 
current for power, but they failed because of the cost and 
the fact that no good working motor had been invented. 

Light and power were needed. Electricity could supply 
both. But how overcome the difficulty of cost, and produce 
an electric current from burning coal or falling water ? For 
answer man looked to the great discovery of Faraday and 
his "new electrical machine." Inventors in Germany, 
France, England, Italy, and America made improvements 
until from the disk dynamo of Faraday there had evolved 
the modern dynamo. 

Electroplating and the telegraph are the only appKca- 
tions of the electric current that became factors in the 

96 



NINETEENTH-CENTURY INVENTIONS 



world's industry before the dynamo, yet in long-distance 
telegraphy and in electroplating to-day the dynamo is used. 
Without the dynamo, electric lighting, electric power, and 
electric traction as developed in the nineteenth century 
would have been impossible; in fact, the dynamo with the 
electric motor (which, as we 
shall see, is only a dynamo 
reversed) is master of the 
field. 

The way had been pre- 
pared for the application 
of Faraday's discovery by 
William Sturgeon, an Eng- 
lishman, and Joseph Henry, 
an American. Sturgeon dis- 
covered that soft iron is 
more quickly magnetized 
than steel, and found that 
the strength of an electro- 
magnet can be greatly in- 
creased by making the core 
of a soft-iron rod and bend- 
ing the rod into the form 
of a horseshoe (Fig. 42) 




AiHfc 



FIG. 42 STURGEON S ELECTRO- 
MAGNET 



The iron rod was coated with 
sealing-wax and wound with a single layer of copper wire, 
the turns of wire not touching. This was in 1825, before 
Faraday discovered the principle of the dynamo. 

Professor Henry still further increased the strength of 
the electromagnet by covering the wire with silk, which 
made it possible to wind several layers of wire on the iron 

97 



THE STORY OF GREAT INVENTIONS 




FIG. 43 AN ELECTROMAGNET WITH MANY TURNS OF INSULATED WIRE 



core, and many times the length of wire that had been 
used by Sturgeon. Fig. 43 shows such a magnet. One of 
Henry's magnets weighed fifty-nine and a half pounds, and 
would hold up a ton of iron. Sturgeon said: *' Professor 
Henry has produced a magnetic force which completely 
eclipses every other in the whole annals of magnetism." 
With Professor Henry's invention the electromagnet was 
ready for use in the dynamo. Fig. 44 shows a strong 
electromagnet. 

A moving magnet causes a current to flow in a coil, but 
a magnet at rest has no effect. A moving magnet is equal 
to a battery. In Faraday's experiments a current was in- 
duced in a coil of wire by moving a magnet in the coil or by 

98 



NINETEENTH-CENTURY INVENTIONS 



making and breaking the circuit in another coil wound on 
the same iron core. A current was induced in a metal disk 
by revolving it between the poles of a magnet. In every 
case there was motion in a magnetic field, or the field itself 
was changed. A changing magnetic field is equal to a 
moving magnet. What 
is needed to induce a 
current in a coil, whether 
it be in a dynamo, an 
induction-coil, or a trans- 
former, is a changing 
magnetic field about the 
coil or motion of the coil 
in the magnetic field. 

If fine iron filings are 
sprinkled over the poles 
of a magnet the filings 
arrange themselves in 
definite lines. This is a 
simple experiment which 
any boy can try for him- 
self. Faraday called the 
lines marked out by the 
iron filings ** lines of 
force" (the lines of force 
of a horseshoe magnet 
are shown in Fig. 36), 

because they indicate the direction in which the mag- 
net pulls a piece of iron — that is, the direction of the 
magnetic force. Now, if a current is to be induced in a 

99 




FIG. 44 AN ELECTROMAGNET LIFTING 

TWELVE TONS OF IRON 



THE STORY OF GREAT INVENTIONS 

wire, the wire must move across the Hnes of force. If 
the wire moves along the Hnes marked out by the iron 
fiHngs, there will be no current. When a coil rotates be- 
tween the poles of a magnet, the wire moves across the lines 
of force and a current is induced in the coil if the circuit is 
closed. This is the way a current is produced in a dynamo. 
Faraday produced a current by rotating a coil between 
the poles of a steel magnet. He made a number of such 
machines, and used them with some success in producing 
lights for lighthouses, but the defects of these machines 
were so great that the lighting of a city or the development 
of power on a large scale was impractical. The electro- 
magnet was needed to solve the problem. 

Siemens' Dynamo 

The war of 1866 between Austria and Prussia and the 
certainty of a coming struggle with France turned the at- 
tention of German inventors to the use of electricity in 
warfare. Werner von Siemens, an artillery officer, was 
improving an exploding device for mines. An electric cur- 
rent was needed to produce a spark or heat a wire to red- 
ness in the powder. Faraday had used a coil of wire turn- 
ing between the poles of a steel magnet to produce a current. 
In England a coil turning between the poles of an electro- 
magnet had been used, but the electromagnet received 
its current from another machine in which a steel magnet 
was used. Siemens found that the steel magnet could be 
dispensed with, and that a coil turning between the poles 
of an electromagnet could furnish the current for the 

100 



NINETEENTH-CENTURY INVENTIONS 

electromagnet. Two things are needed, then, to make a 
dynamo: an electromagnet and a coil to turn between 
the poles of that magnet. The rotating coil, which usually 
contains a soft-iron core, is called the " armature." The 
coil will furnish current for the magnet and some to spare ; 
in fact, only a small part of the current induced in the coil 
is needed to keep the magnet up to its full strength, and the 
greater part of the current may be used for lighting or 




FIG. 45 — A DYNAMO WITH SIEMENS' ARMATURE 
lOI 



THE STORY OF GREAT INVENTIONS 

power. The new machine was named by its inventor " the 
dynamo-electric machine." The name has since been short- 
ened to "dynamo." The first practical problem which the 
dynamo solved was the construction of an electric explod- 
ing apparatus without the use of steel magnets or bat- 
teries. A dynamo with Siemens' armature is shown in Fig. 45 . 




FIG. 46 RING ARMATURE 



In his first enthusiasm the inventor dreamed of great 
things for the new machine, among others an electric street 
railway in Berlin. But the dynamo was not yet ready. 
The difficulty was the heating of the iron core of the arma- 
ture, caused by the action of induced currents. There are 
induced currents in the iron core as well as in the coil, and, 
for the same reason, the coil and the iron core within it are 
both moving in a magnetic field. These little currents circling 



NINETEENTH-CENTURY INVENTIONS 




FIG. 47 FIRST DYNAMO PATENTED IN THE UNITED STATES 

Intended to be used for killing whales. 

Photo by Claudy. 

round and round in the iron core produce heat. The rapid 
changing of the magnetism of the iron also heats the iron. 
It remained for Gramme, in France, to apply the proper 
remedy. This remedy was an armature in which the coil 
was wound on an iron ring, invented by an Italian, Pacinotti. 
Gramme applied the principle discovered by Siemens to 
Pacinotti 's ring, and produced the first practical dynamo for 
strong currents. This was in 1868. A ring armature is 
shown in Fig. 46. The first dynamo patented in the United 
States is shown in Fig. 47. This dynamo is only a curiosity. 

103 



THE STORY OF GREAT INVENTIONS 



The Drtjm Armatttre 

An improvement in the Siemens armature was made four 
years later by Von Hefner- Alteneck, an engineer in the em- 
ploy of Siemens. This improvement consisted in winding 
on the iron core a number of coils similar to the one coil of 
the Siemens armature, but wound in different directions. 
This is called the "drum armature" (Fig. 48). The heating 

of the core is prevented 
by building it up of a 
number of thin iron 
plates insulated from 
one another and by air- 
spaces within the core. 
The insulation prevents 
the small currents from 
flowing around in the 
core. The air - spaces 
serve for cooling. The 
drum armature was a 
great improvement over 
both the Siemens and 
the Gramme armatures. 
With the Siemens one- 
coil armature there is a point in each revolution at 
which there is no current. The current, therefore, varies 
during each revolution of the armature from zero to full 
strength. In the Gramme armature only half the wire, 
the part on the outside of the ring, receives the full 
effect of the magnetic field. The inner half is practically 

104 




FIG. 48 A DRUM ARMATURE, SHOWING 

HOW AN ARMATURE OF FOUR 
COILS IS WOUND 



NINETEENTH-CENTURY INVENTIONS 

useless, except to carry the current which is generated in 
the outer half. Both these difficulties are avoided in the 
drum armature. The dynamos of to-day are modifications 
of the two kinds invented by Siemens and Gramme » Many 
special forms have been designed for special kinds of work. 

Edison's Compound- Wotind Dynamo 

Edison, in his work on the electric light and the electric 
railway, made some important improvements in the dynamo. 
The armature of a dynamo is usually turned by a steam- 
engine. Edison found that much power was wasted in the 
use of belts to connect the engine and the dynamo. He 
therefore connected the engine direct to the dynamo, 
placing the armature of the dynamo on the shaft of the 
engine. He also used more powerful field - magnets than 
had been used before. His greatest improvement, how- 
ever, was in making the dynamo self-regulating, so that 
the dynamo will send out the strength of current that is 
needed. Such a dynamo will send out more current when 
more lights are turned on. Whether it supplies current 
for one light or a thousand, it sends out just the current 
that is needed — no more, no less. It will do this if no hu- 
man being is near. An attendant is needed only to keep 
the machinery well oiled and see that each part is in work- 
ing order. Edison brought about this improvement by his 
improved method of winding. This method is known as 
"compound winding." 

To understand compound winding we must first under- 
stand two other methods of winding. In the series wind- 



THE STORY OF GREAT INVENTIONS 

ing (Fig. 49), all the current generated in the armature flows 
through the coils of the field-magnet. There is only one 
circuit. The same current flows through the coils of the 




FIG. 49 A SERIES-WOUND DYNAMO 

magnet and through the outer circuit, which may contain 
lights or motors. Such a dynamo is commonly used for 
arc lights. It will not regulate itself. If left to itself it will 
give less electrical pressure when more pressure is needed. 
It requires a special regulator. 

In the second form of winding the current is divided into 

106 



NINETEENTH-CENTURY INVENTIONS 

two branches. One branch goes through the coils of the 
field-magnet. The other branch goes through the line wire 
for use in lights or motors. This is called the *' shunt wind- 
ing " (Fig. 50) . The shunt-wound dynamo is used for incan- 
descent lights. It also requires a special regulator, for if left 




FIG. 50 A SHUNT-WOUND DYNAMO 



to itself it gives less electrical pressure when the pressure 
should be kept the same. 

The compound winding (Fig. 51), which was first used by 
Edison, is a combination of the series and shunt windings. 



107 



THE STORY OF GREAT INVENTIONS 




FIG, 5 1 A COMPOUND-WOUND DYNAMO 

The current is divided into two branches. One branch goes 
only through the field-coils. The other branch goes through 
additional coils which are wound on the field-magnet, and 
also through the external circuit. Such a dynamo can be 
made self -regulating, so that it will give always the same 
electrical pressure whatever the number of lamps or motors 
thrown into the circuit. In maintaining always the same 
pressure it of course supplies more or less current, accord- 
ing to the amount of current that is needed. This is clear 
if we compare the flow of electric current with the flow of 
water. Open, a water-faucet and notice how fast the water 
flows. Then open several other faucets connected with the 
same water-pipe. Probably the water will not flow so fast 
from the first faucet. That is because the pressure has 
been lowered by the flow of water from the other faucets. 
If we could make the water adjust its own pressure and 
keep the pressure always the same, then the water would 
always flow at the same rate through a faucet, no matter 

io3 




FIG. 52 ONE OF EDISON S FIRST DYNAMOS 

Permission of Association of Edison Illuminating Companies. 



THE STORY OF GREAT INVENTIONS 

how many other faucets were opened. This is what hap- 
pens in the Edison compound-wound dynamo. Turn on 
one i6-candle-power carbon lamp. It takes about half an 
ampere of current. Turn on a hundred lamps connected 
to the same wires, and the dynamo of its own accord keeps 
the pressure the same, and supplies fifty amperes, or half 




FIG. 53 A DYNAMO MOUNTED ON THE TRUCK OF A RAILWAY CAR 

The dynamo furnishes current for the electric hghts in the car. When 
the train is not running the current is furnished by a storage battery. 



an ampere for each lamp. With this invention of Edison 
the dynamo was practically complete, and ready to furnish 
current for any purpose for which current might be needed. 
Fig. 52 shows one of Edison's first dynamos. Fig. 53 shows 
a dynamo used for lighting a railway coach. 



no 



NINETEENTH-CENTURY INVENTIONS 

Electric Power 

It has been said that the nineteenth century was the age 
of steam, but the twentieth will be the age of electricity. 
Before the end of the nineteenth century, however, electric 
power had become a reality, and there remained only de- 
velopment along practical lines. 

We must turn to Oersted, Ampere, and Faraday to find 
the beginning of electric power. In Oersted's experiment, 
motion of a magnet was produced by an electric current. 
Ampere found that electric currents attract or repel each 
other, and this because of their magnetic action. Faraday 
found that one pole of a magnet will spin round a wire 
through which a current is flowing. Here was motion pro- 
duced by an electric current. These great scientists dis- 
covered the principles that were applied later by inventors 
in the electric motor. 

A number of motors were invented in the early years of 
the century, but they were of no practical use. It was not 
until after the invention of the Gramme and Siemens 
dynamos that a practical motor was possible. It was found 
that one of these dynamos would run as a motor if a current 
were sent through the coils of the armature and the field- 
magnet; in fact, the current from one dynamo may be 
made to run another similar machine as a motor. Thus 
the dynamo is said to be reversible. If the armature is 
turned by a steam-engine or some other power, a current 
is produced. If a current is sent through the coils, the 
armature turns and does work. If the machine is used to 
supply an electric current, it is a dynamo. If used to do 

8 III 



THE STORY OF GREAT INVENTIONS 

work — as, for example, to propel a street-car and for that 
purpose receives a current — it is a motor. The saine ma- 
chine may be used for either purpose. In practice there are 
some differences in the winding of the coils of dynamos and 
motors, yet any dynamo can be used as a motor and any 
motor can be used as a dynamo. This discovery made it 
possible to transmit power to a distance with little waste 
as well as to divide the power easily. The current from 
one large dynamo may light streets and houses, and at the 
same time run a number of motors in factories or street- 
cars at great distances apart. A central-station dynamo 
may run the motors that propel hundreds of street -cars. 
Dynamos at Niagara furnish current for motors in Buffalo 
and other cities. One great scientist, who no doubt fore- 
saw the wonders of electricity which we know so well 
to-day, said that the greatest discovery of the nineteenth 
century was that the Gramme machine is reversible. 

The First Electric Railway 

The electric railway was made possible by the invention 
of the dynamo and the discovery that the dynamo is re- 
versible. At the Industrial Exposition in Berlin in 1879 
there was exhibited the first practical electric locomotive, 
the invention of Doctor Siemens. The locomotive and its 
passenger-coach were absurdly small. The track was cir- 
cular, and about one thousand feet in length. This diminu- 
tive railway was referred to by an American magazine as 
"Siemens' electrical merry-go-round." But the electrical 
merry-go-round aroused great interest because of the pos- 
sibilities it represented (Fig. 54). 

112 



THE STORY OF GREAT INVENTIONS 

The current was generated by a dynamo in Machinery 
Hall, this dynamo being run by a steam-engine. An exact- 
ly similar dynamo mounted on wheels formed the locomotive. 
The current from the dynamo in Machinery Hall was used 
to run the other as a motor and so propel the car. The 
rails served to conduct the current. A third rail in the 
middle of the track was connected to one pole of the dynamo 
and the two outer rails to the other pole. A small trolley 
wheel made contact with the third rail. The rails were not 
insulated, but it was found that the leakage current was 
very small, even when the ground was wet. 

The success of this experiment aroused great interest, 
not only in Germany, but in Europe and America. America's 
greatest inventor, Edison, took up the problem. Edison em- 
ployed no trolley line or third rail, but only the two rails of 
the track as conductors, sending the current out through one 
rail and back through the other. Of course, this meant that 
the wheels must be insulated, so that the current could flow 
from one rail to the other only through the coils of the motor. 

As in Siemens' experiment, the motor was of the same 
construction as the dynamo. The rails were not insulated, 
and it was found that, even when the track was wet, the 
loss of electric current was not more than 5 per cent. Edison 
found that he could realize in His motor 70 per cent, of the 
power applied to the dynamo, whereas the German inventor 
was able to realize only 60 per cent. The improvement was 
largely due to the improved winding. Edison was the first 
to use in practical work the compound- wound dynamo, and 
this was done in connection with his electric railway. Fig. 
55 shows Edison's first electric locomotive. 

114 



THE STORY OF GREAT INVENTIONS 

The question of gearing was a troublesome one. The 
armature shaft of the motor was at first connected by- 
friction gearing to the axle of two wheels of the locomotive. 
Later a belt and pulleys were used. An idler pulley was 
used to tighten the belt. When the motor was started and 
the belt quickly tightened the armature was burned out. 
This happened a number of times. Then Mr. Edison brought 
out from the laboratory a number of resistance - boxes, 
placed them on the locomotive, and connected them in 
series with the armature. These resistances would permit 
only a small current to flow through the motor as it was 
starting, and so prevent the burning-out of the armature 
coils. The locomotive was started with the resistance-boxes 
in circuit, and after gaining some speed the operator would 
plug the various boxes out of circuit, and in that way in- 
crease the speed. When the motor is running there is a 
back-pressure, or a pressure that would cause a current to 
flow in the opposite direction from that which is running 
the motor. Because of this back - pressure the current 
which actually flows through the motor is small, and the 
resistance-boxes may be safely taken out of the circuit. 
Finding the resistance - boxes scattered about under the 
seats and on the platform as they were a nuisance, Mr. Edison 
threw them aside, and used some coils of wire wound on the 
motor field-magnet which could be plugged out of the circuit 
in the same way as the resistance-boxes. This device of Edi- 
son's was the origin of the controller, though in the controller 
now used on street-cars not only is the resistance cut out as 
the speed of the car increases, but the electrical connections 
of the motor are changed in such a way as to increase its 

ii6 



THE STORY OF GREAT INVENTIONS 

speed gradually. Fig. 56 shows Edison's first passenger loco- 
motive. 

The news of the little electric railway at the Industrial 
Exposition in Berlin was soon noised abroad, and the Ger- 
man inventor received inquiries from all parts of the world, 
indicating that efforts would be made in other countries 
to develop practical electrical railways. The firm of Sie- 
mens & Halske therefore determined to build a line for 
actual traffic, not for profit, but that Germany might have 
the honor of building the first practical electric railway. The 
line was built between Berlin and Lichterfelde, a distance 
of about one and a half miles. A horse-car seating twenty- 
six persons was pressed into service. A motor was mounted 
between the axles, and a central- station dynamo exactly 
like the motor was installed. As in Edison's experimental 
railway, the two rails of the track were used to carry the 
current. This electric line replaced an omnibus line, and 
was immediately used for regular traffic, and thus the electric 
railway was launched upon its remarkable career. The first 
electric car used for commercial service is shown in Fig. 57. 

Electric Lighting 

From the time when the night-watchman carried a 
lantern to the time of brilliantly lighted streets was less 
than a century. It was a time when the rapid growth of 
railways and commerce brought about a rapid growth of 
cities, and with the growth of cities the need of illumina- 
tion. Factories must run at night to meet the world's de- 
mands. Commerce cannot stop when the sun sets. The 
centres of commerce must have light. 

118 



NINETEENTH-CENTURY INVENTIONS 

During this time scientists were at work in their labora- 
tories developing means for producing a high vacuum. They 
were able to pump the air out of a glass bulb until less than 
a millionth part of the air remained. They little dreamed 
that there was any connection between the high vacuum 
and the problem of lighting. Discoverers were at work 




FIG. 57 FIRST COMMERCIAL ELECTRIC RAILWAY 

An old horse-car converted into an electric car. 



bringing to light the principles now utilized in the dynamo. 
In the fulness of time these factors were brought together 
to produce an efficient system of lighting. 

For a time gas replaced the lantern of the night-watchman, 
only to yield the greater portion of the field to its rival, 
electricity. 

119 



THE STORY OF GREAT INVENTIONS 



The first efforts were in the direction of the arc light. 
From the earliest times the light given out by an electric 
spark had been observed. It was the aim of inventors to 
produce a continuous spark that should give out a brilliant 
light. It was thought for a time that the electric battery 
would solve the problem, but the cost of the battery cur- 
rent was too great. Again we are indebted to Faraday, for 
it was the dynamo that made electric lighting possible. 

An arc light is produced by an electric current flowing 
across a gap between two sticks of carbon. The air offers 
very great resistance to the flow of electric current across 
this gap. Now whenever an electric current flows through 
something which resists its flow, heat is produced. The 
high resistance of the air-gap causes such intense heat that 
the tips of the carbons become white hot and give out a 
brilliant light. If examined through a smoked glass a beau- 
tiful blue arc of carbon vapor may be seen between the 
carbon tips. If the current flows in one direction only, 
one of the carbons, the positive, becomes hotter and brighter 
than the other. 

In 1878 the streets of Paris were lighted with the ''Jab- 
lochkoft" candle," a form of arc light supplied with current 
by the Gramme machine. In the same year the Brush 
system of arc lighting was given to the public. This was 
the beginning of our present system of arc lighting. 

The electric arc is suitable for hghting streets and for 
large buildings, but cannot be used for lighting houses. 
The light is too intense. One arc would furnish enough 
light for a number of houses if the light could be divided 
so that there might be just the right amount of light in 

120 



NINETEENTH-CENTURY INVENTIONS 

each room. But this is impossible with the electric arc. 
The Edison system of incandescent lighting was required to 
solve the problem of lighting houses by electricity. 

In 1880 the Edison system was brought out for commercial 
use. Edison's problem was to produce a light that could 
be divided into a number of small lights, and one that 
would require less attention than the arc light. He tried 
passing a current through platinum wire enclosed in a 
vacuum. This gave a fairly good light, but was not wholly 
satisfactory. He sat one night thinking about the problem, 
unconsciously fingering a bit of lampblack mixed with tar 
which he had used in his telephone. Not thinking what he 
was doing, he rolled this mixture of tar and lampblack into 
a thread. Then he noticed what he had done, and the 
thought occurred to him: ''Why not pass an electric cur- 
rent through this thread of carbon?" He tried it. A faint 
glow was the result. He felt that he was on the right track. 
A piece of cotton thread must be heated in a furnace in an 
iron mold, which would prevent the thread from burning 
by keeping out the air. Then all the other elements that 
were in the thread would be driven out and only the carbon 
remain. For three days he worked without sleep to pre- 
pare this carbon filament. At the end of two days he suc- 
ceeded in getting a perfect filament, but when he attempted 
to seal it in the glass bulb it broke. He patiently worked 
another day, and was rewarded by securing a good carbon 
filament, sealed in a glass globe. He pumped the air out of 
this globe, sealed it, and sent a current through the carbon 
thread. He tried a weak current at first. There was a 
faint glow. He increased the current. The thread glowed 



NINETEENTH-CENTURY INVENTIONS 

more brightly. He continued to increase the current until 
the slender thread of carbon, which would crumble at a 
touch, was carrying a current that would melt a wire of 
platinum strong enough to support a weight of several 
pounds. The carbon gave a bright light. He had found 
a means of causing the electric current to furnish a large 
number of small lights. Fig. 58 is an excellent photograph 




Copyright, 1904, by William J. Hammer 

59 — Edison's famous horseshoe paper-filament lamp of 1870 



of Edison at work in his laboratory. Fig. 59 shows some of 
Edison's first incandescent lamps. He next set out in 
search of the best kind of carbon for the purpose. He car- 
bonized paper and wood of various kinds — in fact, every- 
thing he could find that would yield a carbon filament. He 
tried the fibres of a Japanese fan made of bamboo, and 
found that this gave a better light than anything he had 
tried before. He then began the search for the best kind 

123 



THE STORY OF GREAT INVENTIONS 

of bamboo. He learned that there are about twelve hun- 
dred varieties of bamboo ; He must have a sample of every 
variety. He sent men into every part of the world where 
bamboo grows. One man travelled thirty thousand miles 
and had many encounters with wild beasts in his search for 
the samples of bamboo. At last a Japanese bamboo was 
found that was better than any other. The search for the 
carbon fibre had cost about a hundred thousand dollars. 
Later it was found that a "squirted filament" could be 
made that worked as well as the bamboo fibre. This was 
made by dissolving cotton wool in a certain solution, and 
then squirting this solution through a small hole into a 
small tank containing alcohol. The alcohol causes the sub- 
stance to set and harden, and thus forms a carbon thread 
the size of the hole. Fig. 60 shows the first commercial 
electric-lighting plant, which was installed on the steamship 
Columbia in 1880. 

The carbon thread in the incandescent light is heated to 
a white heat, and because it is so heated it gives out light. 
In air such a tiny thread of white-hot carbon would burn 
in a fraction of a second. The carbon must be in a vacuum, 
and so the air is pumped out of the light bulb with a special 
kind of air-pump invented not long before Edison began 
his work on the electric light. This pump is capable 
of taking out practically all the air that was in the bulb. 
Perhaps a millionth part of the original air remains. 

A great invention is never completed by one man. It 
was to be expected that the electric light would be im- 
proved. A number of kinds of incandescent light have been 
devised, using different kinds of filaments 9,nd adapted to 

124 



NINETEENTH-CENTURY INVENTIONS 




FIG. 6c 



-FIRST COMMERCIAL EDISON ELECTRIC-LIGHTING PLANT; INSTALLED 
ON THE STEAMSHIP "COLUMBIA " IN MAY. 1880 



a variety of uses. The original Edison carbon lamp, how- 
ever, continues in use, being better adapted to certain pur- 
poses than the newer forms. 

The mercury vapor light deserves mention as a special 
form of arc light. In the ordinary arc light the arc is 
formed of carbon vapor, and the light is given out from the 
tips of the white-hot carbons. In the mercury vapor light 
the light is given out from the mercury vapor which forms 
the arc. This arc may be of any desired length, and yields 
a soft, bluish-white light which is a near approach to day- 



light. 



125 



THE STORY OF GREAT INVENTIONS 

The Telegraph 

The need of some means of giving signals at a distance 
was early felt in the art of war. Flag signals such as are 
now used by the armies and navies of the world were intro- 
duced in the middle of the seventeenth century by the 
Duke of York, admiral of the English fleet, who afterward 
became James 11. of England. Other methods of com- 
municating at a distance were devised from time to time, 
but the distance was only that at which a signal could be 
seen or a sound heard. No means of communicating over 
very long distances was possible until the magnetic action 
of an electric current was discovered. When Oersted's dis- 
covery was made known men began to think of signalling to 
a distance by means of the action of an electric current on 
a magnetic needle. A current may be sent over a very 
long wire, and it will deflect a magnetic needle at the other 
end. The movements of the needle may be controlled by 
opening and closing the circuit, and a system of signals or 
an alphabet may be arranged. A number of needle tele- 
graphs were invented, but they were too slow in action. 
Two other great inventions were needed to prepare the 
way for the telegraph. One was the electromagnet in the 
form developed by Professor Henry, a horseshoe magnet 
with many turns of silk-covered wire around the soft-iron 
core, so that a very feeble current will produce a magnet 
strong enough to move an armature of soft iron. The mag- 
net has this strength because the current flows so many 
times around the iron core. Another need was that of a 
battery that could be depended on to give a constant cur- 

126 



NINETEENTH-CENTURY INVENTIONS 

rent for a considerable length of time. This need was met 
by the Daniell cell. 

The electromagnet made the telegraph possible. The 
locomotive made it a necessity. Without the telegraph it 
would be impossible to control a railway system from a 
central office. A train after leaving the central station 
would be like a ship at sea before the invention of the wire- 
less telegraph. Nothing could be known of its movements 
until it returned. The need of a telegraph was keenly felt 
in America when the new republic was extended to the 
Pacific Coast. An English statesman said, after the United 
States acquired California, that this marked the end of the 
great American Republic, for a people spread over such a 
vast area and separated by such natural barriers could 
not hold together. He did not know that the iron wire 
of the telegraph would bind the new nation firmly to- 
gether. 

The Morse telegraph system now in use throughout the 
civilized world was made possible by the work of Sturgeon 
and Henry. Sturgeon's electromagnet might have been 
used for telegraphy through very short distances, but 
Henry's magnet, with its coils of many turns of insulated 
wire, was needed for long-distance signalling. In one of 
the rooms of the Albany Academy, Professor Henry caused 
an electromagnet to sound a bell when the current was 
transmitted through more than a mile of wire. This might 
be called the first electromagnetic telegraph. But the ap- 
plication to actual practice was made by Morse, and the 
man who first makes the practical application of a prin- 
ciple is the true inventor. 

9 127 



THE STORY OF GREAT INVENTIONS 

In 1832, on board the packet-ship Sully, Samuel F. B. 
Morse, an American artist, forty-one years of age, was re- 
turning from Europe. In conversation a Doctor Jackson 
referred to the electrical experiments of Ampere, which he 
had witnessed while in Europe, and, in reply to a question, 
said that electricity passes instantaneously over any known 
length of wire. The thought of transmitting words by 
means of the electric current at once took possession of the 
artist's mind. After many days and sleepless nights he 
showed to friends on board the drawings and notes he had 
made of a recording telegraph. 

In New York, in a room provided by his brothers, he 
gave himself up to the working-out of his idea, sleeping 
little and eating the simplest food. Receiving an appoint- 
ment as professor in the University of the City of New 
York, he moved to one of the buildings of that university 
and continued his experiments in extreme poverty, and at 
times facing starvation, as his salary depended on the tui- 
tion fees of his pupils. 

A story told by one of his pupils describes his condition 
at the time. 

"I engaged to become one of Morse's pupils. He had 
three others. I soon found that the professor had little 
patronage. I paid my fifty dollars; that settled one quar- 
ter's tuition. I remember, when the second was due, my 
remittance from home did not come as expected, and one 
day the professor came in and said, courteously: 

" ' Well, Strother, my boy, how are we off for money?' 
Why, professor, I am sorry to say I have been disap- 
pointed; but I expect a remittance next week.' 

128 



NINETEENTH-CENTURY INVENTIONS 

'''Next week!' he repeated, sadly; 'I shall be dead by 
that time.' 

'"Dead, sir?' 

"'Yes; dead by starvation!' 

"I was distressed and astonished. I said, hurriedly: 
'Would ten dollars be of any service?' 

'"Ten dollars would save my life; that is all it would 
do.'" 

The money was paid, all the student had, and the two 
dined together. It was Morse's first meal in twenty-four 
hours. 

The Morse telegraph sounder (Fig. 6i) consists of an 




FIG. 6l A TELEGRAPH SOUNDER 



electromagnet and a soft-iron armature. When no current 
is flowing the armature is held away from the magnet by a 
spring. When the circuit is closed a current flows through 



129 



THE STORY OF GREAT INVENTIONS 

the coils of the magnet and the armature is attracted, caus- 
ing a cHck. When the circuit is broken the spring pulls the 
armature away from the magnet, causing another click. 
The circuit is made and broken by means of a key at the 
other end of the line. In Morse's first instrument (Fig. 62) 
the armature carried a pen, which was drawn across a rib- 
bon of paper when the armature was attracted by the magnet. 
If the pen was held by the magnet for a very short time, a 
dot was made ; if for a longer time, a dash. The pen was 
soon discarded, and the message taken by sound only. 
The Morse alphabet now in use was devised by a Mr. Vail, 
who assisted Morse in developing the telegraph. The 
thought occurred to Mr. Vail that he could get help from 
a printing-ofhce in deciding the combinations of dots and 
dashes that should be used for the different letters. The 
letters requiring the largest spaces in the type-cases are 
the ones that occur most frequently, and for these letters 
he used the simplest combinations of dots and dashes. 

Morse repeatedly said that, if he could make his telegraph 
work through ten miles, he could make it work around the 
world. This promise of long-distance telegraphy he ful- 
filled by the use of the relay. The relay works in the same 
way as the sounder. The current coming over a long line 
may be too feeble to produce a click that can be easily 
heard, yet strong enough to magnetize the coils of the relay 
and cause the armature to close another circuit. This 
second circuit includes the sounder and a battery in the 
same station as the sounder, which we shall call "the local 
battery." The relay simply acts as a contact key, and closes 
the circuit of the local battery. Thus the current from the 

130 



V ,. , — 


■"-^mg" 


':*® 


i 

< 


^^^^^^ 




- 






■■L 


i 




■■i^^,i».«^ 


1 




1 



FIG. 62 morse's first TELEGRAPH INSTRUMENT 

A pen was attached to the pendulum and drawn across the strip of 
paper by the action of the electromagnet. The lead type shown in the 
lower right-hand corner was used in making electrical contact when send- 
ing a message. The modern instrument shown in the lower left-hand cor- 
ner is the one that sent a message around the world in 1896. 

Photo by Claudy. 



THE STORY OF GREAT INVENTIONS 

local battery flows through the sounder and produces a 
loud click. Sometimes a relay is used to control a second 
very long circuit. At the farther end of the second circuit 
may be a sounder or a second relay which controls a third 
circuit. Any number of circuits may be thus connected 
by means of relays. This is a form of repeating system 
used for telegraphing over very long distances. Fig. 63 
shows a circuit with relay and sounder. 

In the telegraphic circuit only one connecting wire is 



a 



-^ SounJer^ 




o 



Lwe wire 




W 



Bdfer/ 



Rela,y 



FIG. 63 A TELEGRAPHIC CIRCUIT WITH RELAY AND SOUNDER 

132 



NINETEENTH-CENTURY INVENTIONS 

needed. The earth, being a good conductor of electricity, 
is used as part of the circuit. It is necessary, therefore, to 
make a ground connection at each end of the hne, the in- 
struments being connected between the Hne wire and the 







Sounc/er 




% 








^ Sounc/er 






















= 




K 




















/r 




^ 












^\' 




^ 


E BMery 


















— , 


— 


_ 









1 


' 1 






^ 


— _ 




Farth 




— ~ 




- 







FIG. 64 A SIMPLE TELEGRAPHIC CIRCUIT 

Two keys are shown at K K, and two switches at S 5. When one key 
is to be used the switch at that station must be open, and the switch 
at the other station closed. 



earth. For long - distance telegraphy a current from a 
dynamo is used instead of a battery current. Fig. 64 shows 
a simple telegraphic circuit. 

A telegraphic message travels with the speed of light, 
for the speed of electricity and the speed of light are the 
same. A telegraphic signal would go more than seven 
times around the earth in one second if it travelled on one 
continuous wire. The relays that must be used, however, 
cause some delay. 

133 



THE STORY OF GREAT INVENTIONS 

In 1835 Morse's experimental telegraph was completed, 
and in 1837 i^ was exhibited to the public, but seven years 
more passed before a line was established for public use. 
Aid from Congress was necessary. Going to Washington, 
Morse exhibited his instrument in the halls of the Capitol, 
sending messages through ten miles of wire wound on a 
reel. The invention was ridiculed, but the inventor did not 
despair. A bill for an appropriation to establish a tele- 
graphic line between Washington and Baltimore passed the 
House by a small majority. The last day of the session 
came. Ten o'clock at night, two hours before adjourn- 
ment, and the Senate had not acted. A senator advised 
Morse to go home and think no more of it, saying that the 
Senate was not in sympathy with his project. He went 
to his hotel, counted his money, and found that he could 
pay his bill, buy his ticket homx, and have thirty-seven 
cents left. All through his work he had firmly believed 
that a Higher Power was directing his work, and bringing 
to the world, through his invention, a new and uplift- 
ing force ; and so when all seemed lost he did not lose 
heart. 

In the morning a friend. Miss Ellsworth, called and of- 
fered her congratulations that the bill had been passed by 
the Senate and thirty thousand dollars appropriated for 
the telegraph. Being the first to bring the news of his 
success, Mr. Morse promised her that the first message over 
the new line should be hers. In about a year the line was 
completed, and Miss Ellsworth dictated the now famous 
message: ''What hath God wrought!" 

Soon afterward the Democratic Convention, in session in 

134 



NINETEENTH-CENTURY INVENTIONS 

Baltimore, received a telegraphic message from Senator 
Silas Wright, in Washington, declining the nomination for 
the Vice-Presidency, which had been tendered him. The 
convention refused to accept a message sent by telegraph, 
and sent a committee to Washington to investigate. The 
message was confirmed, and Morse and his telegraph be- 
came famous. Fig. 65 shows the first telegraph instrument 
used for commercial work. 

The desire to telegraph across the ocean came with the 




FIG. 65 FIRST TELEGRAPH INSTRUMENT USED FOR COMMERCIAL WORK 

Photo by Claudy. 



introduction of the telegraph on land. Bare wires in the 
air with glass insulators at the poles are used for land teleg- 
raphy, but bare wires in the water could not be used, for 
ocean water will conduct electricity. Something was needed 
to cover the wire, protect it from the water, and prevent 
the escape of the electric current. Just when it was needed 

135 



THE STORY OF GREAT INVENTIONS 

such a substance was discovered. In 1843, when Morse was 
working on his telegraph, it was found that the juice of a cer- 
tain kind of tree growing in the Malayan Archipelago formed 
a substance somewhat like rubber but more durable, and 
especially suited to the insulation of wires in water. This 
substance is gutta-percha. Ocean cables are made of a 
number of copper wires, each wire covered with gutta- 
percha, the wires twisted together and protected with tarred 
rope yam and an outer layer of galvanized iron wires. The 
earth is used for the return circuit, as in the land telegraph. 

Dttplex Telegraphy 

The telegraph was a success, but many improvements 
were yet to be made. Economy of construction was the 
thing sought for. To make one wire do the work of two 
was accomplished by the invention of the duplex system. 
In duplex telegraphy two messages may be sent in opposite 
directions over the same wire at the same time. Let us 
take a look at some of the methods by which this is accom- 
plished. 

One method with a long name but very simple in its 
working is the differential system (Fig. 66). In the differ- 
ential system the current from the home battery divides 
into two branches passing around the coils of the electro- 
magnet in opposite directions. Now if these two branches 
are so arranged that the currents flowing through them are 
equal, the relay will not be magnetized, because one cur- 
rent would tend to make the end A a north pole, and the 
other current would tend to make the same end a south 

136 




K 




THE STORY OF GREAT INVENTIONS 

pole. The result is that the relay coil is not magnetized, 
and does not attract the armature. But the current from 
the distant battery comes over one of these branches only, 
and will magnetize the relay. Hence, with a similar ar- 
rangement at the second station, two messages may be 
sent at the same time in opposite directions. 

Another method not quite so simple in principle is the 
bridge method. When the key at station A (see Fig. 67) 
is closed, the current from the battery at station A divides 
at C, and if the resistances i and 2 are equal, and the re- 
sistance J is equal to the resistance of the line, no current 
will flow through the sounder. But if a current comes over 
the line from the distant station this current divides at D, 
and a part goes through the sounder, causing it to click. 
The sounder is not affected, therefore, by the current from 
the home battery, but is affected by the current from the 
distant battery. Therefore, a message may be sent and 
another received at the same time. If there is a similar 
arrangement at the other station, two messages may travel 
over the line in opposite directions at the same time. 

The differential method is used in land telegraphy, the 
bridge method almost exclusively in submarine telegraphy. 
The next step was a quadruplex system, by means of which 
four messages may be transmitted over one wire at the 
same time. The first quadruplex system was invented by 
Edison in 1874, and in four years it saved more than half 
a million dollars. Other systems have been invented which 
make it possible to send even a larger number of messages 
at one time over a single wire. 




I\ 

I 



Kb 

§■ 



THE STORY OF GREAT INVENTIONS 

The Telephone 

The idea of "talking by telegraph" began to grow in the 
minds of inventors soon after the Morse instrument came 
into use. The sound of the voice causes vibrations in the 
air. (This is simply shown in the string telephone. This 
telephone is made by stretching a thin membrane, such as 
thin sheepskin, or gold-beaters' skin, over a round frame 
of wood or metal. Two such instruments are connected by 
a string, the end of the string being fastened to the middle 
of the stretched membrane. The sound of the voice causes 
this membrane to vibrate. As the membrane moves rapid- 
ly back and forth, it pulls and releases the string, and so 
causes the membrane at the other end to vibrate and give 
out the sound. This is the actual carrying of the sound 
vibrations along the string) In the telephone it is not 
sound vibrations but an electric current that travels over 
the line wire. The telephone message, therefore, travels 
with the speed of electricity, not with the speed of sound. 
If it travelled with the speed of sound in air, a message 
spoken in Chicago would be heard in New York one hour 
later ; but we know that a message spoken in Chicago may 
be heard in New York the instant it is spoken. 

fThe telephone, like the telegraph, depends on the electro- 
magnet. The thought of inventors at first was to make 
the vibrations of a thin membrane, caused by the sound of 
the voice, open and close a telegraphic circuit. An electro- 
magnet at the other end of the line would cause a thin 
membrane with a piece of soft iron attached to it to vibrate, 
just as the magnet in the telegraph receiver pulls and re- 

140 



NINETEENTH-CENTURY INVENTIONS 

leases the soft-iron armature as the circuit is made and 
broken. The thin membrane caused to vibrate in this way 
would give out the sound. A telephone on this principle 
was invented by Philip Reis, a schoolmaster in Germany. 
The transmitter was carved out of wood in the shape of a 
human ear, the thin membrane being in the position of the 
ear-drum. Musical sounds and even words were trans- 
mitted by this telephone, but it could never have been 
successful as a practical working telephone. The mem- 
brane in the receiver would vibrate with the same speed 
as the membrane in the transmitter, but sound depends 
on something more than speed of vibration.) 
^ The Bell telephone, as known to-day, began with a study 
of the human ear. Alexander Graham Bell was a teacher 
of the deaf. His aim was to teach the deaf to use spoken 
language, and for this purpose he wished to learn the nature 
of the vibrations caused by the voice. His plan was to 
cause the ear itself to trace on smoked glass the waves pro- 
duced by the different letters of the alphabet, and to use 
these tracings in teaching the deaf. Accordingly, a human 
ear was mounted on a suitable support, the stirrup-bone 
removed, leaving two bones attached, and a stylus of wheat 
straw attached to one of the bones. The ear-drum, caused 
to vibrate by the sound, moved the two small bones and 
the pointer of straw, so that when he sang or talked to the 
eai* delicate tracings were made on the glass. 

This experiment suggested to Mr. Bell that a membrane 
heavier than the ear-drum would move a heavier weight. 
If the ear-drum, no thicker than tissue-paper, could move 
the bones of the ear, a heavier membrane might vibrate 

141 



THE STORY OF GREAT INVENTIONS 

a piece of iron in front of an electromagnet. He was at the 
same time devising a telegraph for transmitting messages 
by means of musical sounds. In this telegraph he was 
using an electromagnet in the transmitter and another 
electromagnet in the receiver. He attached the soft-iron 
armature of each electromagnet to a stretched membrane 
of gold-beaters' skin, expecting that the sound of his voice 
would cause the membrane of the transmitter to vibrate, 
and that, by means of the electromagnets, the membrane 
of the receiver would be made to vibrate in the same way 
(Fig. 68). At first he was disappointed, but after making 




FIG. 68 FIRST BELL TELEPHONE RECEIVER AND TRANSMITTER 

The receiver is on the left in the picture. A thin membrane of gold- 
beaters' skin tightly stretched and fastened with a cord can be seen on 
the end of the transmitter and of the receiver. An electromagnet is also 
shown over each membrane. This thin membrane, with a piece of soft iron 
attached, was used in place of the soft-iron disk of the modern receiver. 

142 



NINETEENTH-CENTURY INVENTIONS 

some changes in the armatures a distinct sound was heard 
in the receiver. Later the membrane was discarded, and 
a thin iron disk used with better effect. ' 

The story of Bell's struggles might seem like the repetition 
of the life story of many another great inventor. He knew 




FIG. 69 A TELEPHONE RECEIVER 

that he had discovered something of great value to the 
world. He devoted his time to the perfecting of the tele- 
phone, neglecting his professional work and finally giving 
it up, that he might give his whole time to his invention. 
He was forced to endure poverty and ridicule. He was 
called "a crank who says he can talk through a wire." 
Men said his invention could never be made practical. 
Even after he succeeded in finding a few purchasers and 
some of the telephones were in actual use, people were slow 
to adopt it. The idea of talking at a piece of iron and hear- 
ing another piece of iron talk seemed like a kind of witchcraft, 
(in the telephone we see another use of the electromagnet. 
A very thin iron disk near the poles of an electromagnet 
forms the telephone receiver (Fig. 69) . An electric current 
travels over the telephone wire. If the current grows 
10 143 



THE STORY OF GREAT INVENTIONS 

stronger, the magnet is made stronger and pulls the disk 
toward it. If the current grows weaker, the magnet be- 
comes weaker and does not pull so hard on the disk. The 
disk then springs back from the magnet. If these changes 
take place rapidly the disk moves back and forth rapidly 
and gives out a sound. The sound of the voice at the 
other end of the line sets the disk in the mouthpiece vibrat- 
ing. The vibrations of this disk cause the changes in the 
electric current flowing over the line-wire, and the changes 
in the electric current cause the disk of the receiver to vi- 
brate in exactly the same way as the disk at the mouth- 
piece. Thus the words spoken into the mouthpiece may 
be heard at the receiver. 

^The transmitter used by Bell was like the receiver. Two 
receivers from the common telephone connected by two 
wires may be used as a telephone without batteries. Fig. 70 
shows a complete telephone made of two receivers con- 
nected by two wires. The disk in one receiver which is now 
used as a transmitter is made to vibrate by the sound of the 
voice. Now when a piece of iron moves back and forth in 
a magnetic field it strengthens and weakens the field. So 
the magnetic field in the transmitter is rapidly changed by 
the movement of the iron disk. Now we have found that 
whenever a coil of wire is in a changing magnetic field a 
current is induced in the coil. The small coil in the trans- 
mitter, therefore, has a current induced in it. We have also 
found that when the magnetic field is made stronger the 
induced current flows in one direction, and when the field 
is made weaker the current flows in the opposite direction. 
Since the field in the transmitter is made alternately stronger 

144 



NINETEENTH-CENTURY INVENTIONS 

and weaker, the current in the coil flows first in one direc- 
tion, then in the opposite direction — that is, we have an 
alternating current. This alternating current, of course. 




FIG. 70 TWO RECEIVERS USED AS A COMPLETE TELEPHONE 



flows over the line-wire and through the coil in the receiver. 
In the receiver the alternating current will alternately 
strengthen and weaken the magnetic field, and as it does so 
the pull of the magnet on the iron disk is strengthened and 
weakened. The iron disk in the receiver, therefore, vi- 
brates in exactly the same way as the disk in the transmit- 
ter, and so gives out a sound just like that which is acting 
on the transmitter, 

145 



THE STORY OF GREAT INVENTIONS 



In the Blake transmitter, which is now commonly used, 
the disk moves a pencil of carbon which presses against 
another pencil of carbon. This varies the pressure between 
the two pencils of carbon. A battery current flows through 
the two carbons, and as the pressure of the carbons changes 
the strength of the current changes. When the carbons are 
pressed together more closely the current is stronger. When 
the pressure is less the current is weaker. We have, then, 
a varying current through the carbons. This current flows 

through the primary coil of an 
induction-coil, the secondary 
being connected to the line- 
wire. Now a current of vary- 
ing strength in the primary 
induces an alternating current 
in the secondary. We have, 
DIAPHRAGM then, an alternating current 
flowing over the line - wire. 
This alternating current acts 
on the magnetic field of the 
receiver in the way described 
before, causing the disk in the 
receiver to vibrate and give 
out the sound. 

For long-distance work a 
carbon-dust transmitter (Fig. 
71) is used. In this there are 
many granules of carbon, so 
that instead of two carbon-points in contact there are many. 
This makes the transmitter more sensitive. 

146 




CARBON 
DUST 



FIG. 7: 



-CARBON-DUST TRANS- 
MITTER 



NINETEENTH-CENTURY INVENTIONS 

The strength of current required for the telephone is very 
small. To transmit a telephone message requires less than 
a hundred -millionth part of the current required for a tele- 
graphic message. The work done in lifting the telephone 
receiver a distance of one foot, if changed into an alternating 
current, would be sufficient to keep up a sound in the re- 
ceiver for a hundred thousand years. Because of its extreme 
sensitiveness the telephone requires a complete wire circuit. 
The earth cannot be used for the return circuit, as in the 
case of the telegraph. Disturbances in the earth, vibra- 
tion, leakage currents from trolley lines, and so forth, would 
interfere seriously with the action of the telephone. \ 

When the telephone was invented it was commonly re- 
marked that it could not take the place of the telegraph 
in commerce, for the latter gave the merchant some evidence 
of a business transaction, while the telephone left no sign. 
There was a time when men feared to trust each other, but 
now large business deals are made by telephone ; products 
of the farm, the factory, and the mine are bought and sold 
in immense quantities without a written contract or even 
the written evidence of a telegram. Thus the telephone has 
developed a spirit of business honor. 

The Phonograph 

The phonograph grew out of the telephone. It is said 
to be the only one of Edison's inventions that came by 
accident, yet only a man of genius would have seen the 
meaning of such an accident. He was singing into the 
mouthpiece of a telephone when the vibrations of the disk 

147 



THE STORY OF GREAT INVENTIONS 

caused a fine steel point to pierce one of his fingers held just 
behind the disk. This set him to thinking. If the sound 
of his voice could cause the disk to vibrate with force 
enough to pierce the skin, would it not make impressions 
on tin-foil, and so make a record of the voice that could 
be reproduced by passing the point rapidly over the same 
impressions? He gave his assistants the necessary in- 
structions, and soon the first phonograph was made. 

This disk in the phonograph is set in vibration by sound 
vibrations in the air in the same way as the disk in the tele- 
phone transmitter. Attached to the disk is a needle-point 
which, of course, vibrates with the disk. If a cylinder with 
a soft surface is turned rapidly under the steel point as it 
vibrates, impressions are made in the cylinder correspond- 
ing to the movements of the disk. The cylinder must move 
forward as it turns, so that its path will be a spiral. If, now, 
the stylus is placed at the starting-point and the cylinder 
turned rapidly the stylus will move rapidly up and down 
as it goes over the indentations in the cylinder, and so cause 
the metal disk to vibrate and give out a sound like that 
received at first. In the earliest phonographs the cylinder 
was covered with tin-foil. Later the so-called ''wax rec- 
ords" came into use. These cylinders are not made of wax, 
but of very hard soap. Fig. 72 shows an instrtiment in 
which the sound of the voice caused a pencil-point to trace 
a wavy line on a cylinder. This instrument may be called 
a forerunner of the phonograph. Fig. 73 shows Edison's 
first phonograph with a modern instrument placed beside 
ilj for comparison. 



THE STORY OF GREAT INVENTIONS 

Gas-Engines 

Cannons are the oldest gas-engines. Indeed, the prin- 
ciple of the cannon is the same as that of the modern gas- 
engine, the piston in the engine taking the place of the 
cannon-ball. The power in each case is obtained by ex- 
plosion — in the cannon the explosion of powder, in the 
engine the explosion of a mixture of air and gas. Pow^der- 
engines with pistons were proposed in the seventeenth cen- 




FIG. 73 EDISON S FIRST PHONOGRAPH AND A MODERN INSTRUMENT 

Photo by Claudy. 



tury, and some were actually built, but it proved too diffi- 
cult to control them, and the idea of the gas-engine was 
abandoned for more than a hundred years. 

The discovery of coal-gas near the close of the eighteenth 
century gave a new impetus to the gas-engine. John Bar- 
ber, an Englishman, built the first actual gas-engine. He 

150 



NINETEENTH-CENTURY INVENTIONS 

used gas distilled from wood, coal, or oil. The gas, mixed 
with the proper proportion of air, was introduced into a tank 
which he called the exploder. The mixture was fired and 
issued out in a continuous stream of flame against the 
vanes of a paddle-wheel, driving them round with great 
force. 

In 1804 Lebon, a French engineer, was assassinated, and 
the progress of the gas-engine set back a number of years, 
for this engineer had proposed to compress the mixture of 
gas and air before firing, and to fire the mixture by an 
electric spark. This is the method used in gas-engines 
to-day. 

The first practical working gas-engine was invented by 
Lenoir, a Frenchman, in i860. From this time to the end 
of the century the gas-engine developed rapidly, receiving 
a new impulse from the increasing demand for the motor- 
car. 

The engine of the German inventors, Otto and Langen, 
brought out in 1876, marked the beginning of a new era. 
The greater number of engines used in automobiles to-day 
are of the kind known as the Otto cycle, or four-cycle, 
engine. This engine is called four-cycle because the piston 
makes four strokes for every explosion. There is one stroke 
to admit the mixture of gas and air to the cylinder, another 
to compress the gas and air, at the beginning of the third 
stroke the explosion takes place, and in the fourth stroke the 
burned-out gases are driven out of the cylinder. The work- 
ing of the four-cycle gas-engine is made clear in Figs. 74, 
75, 76, and 77. 

In such a gas-engine the power is applied to the piston 

151 




FIG. 74 FIRST STROKE. GAS AND AIR ADMITTED TO THE CYLINDER 




FIG. 75 SECOND STROKE. MIXTURE OF GAS AND AIR COMPRESSED 




FIG. 76 THIRD STROKE. THE MIXTURE IS EXPLODED AND EXPANDS, 

DRIVING THE PISTON FORWARD 




FIG. 77 FOURTH STROKE, EXHAUST. THE BURNED-OUT MIXTURE OF 

GAS AND AIR EXPELLED FROM THE CYLINDER 



THE FOUR-CYCLE GAS-ENGINE 



NINETEENTH-CENTURY INVENTIONS 

only in one stroke out of every four, while in the steam- 
engine the power is applied at every stroke. It would seem, 
therefore, that a steam-engine would do more work than a 
gas-engine for the same amount of heat, but such is not the 
case ; in fact, a good gas - engine will do about twice as 
much work as a good steam-engine for the same amount of 
fuel. The reason is that the steam-engine wastes its heat. 
Heat is given to the condenser, to the iron of the boiler, to 
the connecting pipes and the air around them, while in the 
gas-engine the heat is produced in the cylinder by the ex- 
plosion and the power applied directly to the piston-head. 
More than this, a steam-engine when at rest wastes heat; 
there must be a fire under the boiler if the engine is to be 
ready for use on short notice. When a gas-engine is at res»t 
there is no fire, nothing is being used up, and yet the engine 
can be started very quickly. A gas-engine can be made 
much lighter than a steam-engine of the same horse-power. 
The automobile and the fiying-machine require very light 
engines. Without the gas-engine the automobile would have 
remained imperfect and crude, while the flying-machine 
would have been impossible. 

In a two-cycle gas-engine there is an explosion for every 
two strokes of the piston, or one explosion for every revo- 
lution of the crank-shaft. During one stroke the mixture 
of gas and air on one side of the piston is compressed and 
a new mixture enters on the opposite side of the piston. 
At the end of this stroke the compressed mixture is ex- 
ploded, and power is applied to the piston during about 
one-fourth of the next stroke. During the remainder of 
the second stroke the burned-out gas escapes, and the fresh 

153 



THE STORY OF GREAT INVENTIONS 

mixture passes over from one side of the piston to the other 
ready for compression. The two-cycle engine is simpler in 
construction than the four-cycle, having no valves. It also 




FIG. 78 TWO-CYCLE GAS-ENGINE. CRANK AND CONNECTING-ROD ARE 

ENCLOSED WITH THE PISTON 



has less weight per horse-power. The cylinder of a two- 
cycle engine is shown in Fig. 78. 

A steam-engine is self-starting. The engineer has only 
to turn the steam into the cylinder, but the gas-engine re- 
quires to be turned until at least one explosion takes place, 
for until there is an explosion of gas and air in the cylinder 
there is no power. 

A gas-engine may have a number of cylinders. Four- 
cylinder and six-cylinder engines are common. In a four- 
cylinder, four-cycle engine, while one cylinder is on the 
power stroke the next is on the compression stroke, the 
third on the admission stroke, and the fourth on the exhaust 
stroke. Fig. 79 shows the Selden ''explosion buggy" pro- 

154 



NINETEENTH-CENTURY INVENTIONS 

pelled by a gas-engine. This machine was the forerunner 
of the modern automobile. 



The Steam Locomotive 

Late in the eighteenth century a mischievous boy put 
some water in a gun-barrel, rammed down a tight wad, and 
placed the barrel in the fire of a blacksmith's forge. The 
wad was thrown out with a loud report, and the boy's play- 
mate, Oliver Evans, thought he had discovered a new 




FIG. 79 SELDEN EXPLOSION BUGGY. FORERUNNER OF THE MODERN 

AUTOMOBILE 



THE STORY OF GREAT INVENTIONS 

power. The prank with the gun-barrel set young Evans 
thinking about the power of steam. It was not long until 
be read a description of a Newcomen engine. In the New- 
comen engine, you will remember, it was the pressure of 
air, not the pressure of steam, that lifted the weight. Evans 
soon set about building an engine in which the pressure of 
steam should do the work. He is sometimes called the 
*'Watt of America," for he did in America much the same 
work that Watt did in Scotland. Evans built the first 
successful non-condensing engine — that is, an engine in 
which the steam, after driving the piston, escapes into the 
air instead of into a condenser. The non-condensing en- 
gine made the locomotive possible, for a locomotive could 
not conveniently carry a condenser. Evans made a loco- 
motive which travelled very slowly. He said, however: 
"The time will come when people will travel in stages 
moved by steam-engines from one city to another, almost 
as fast as birds can fly, fifteen or twenty miles an hour." 

The inventor who made the first successful locomotive 
was George Stephenson, and it is worth noting that one of 
his engines^ the "Rocket," possessed all the elements of 
the modern locomotive. He combined in the ** Rocket" 
the tubular boiler, the forced draft, and direct connec- 
tion of the piston-rod to the crank-pin of the driving- 
wheel. 

The "Rocket" was used on the first steam railway (the 
Stockton & Darlington, in England) , which was opened in 
1825. There had been other railways for hauling coal by 
means of horses over iron tracks, and other locomotives that 
travelled over an ordinary road ; but this was the first road 

156 



NINETEENTH-CENTURY INVENTIONS 

on which a steam-engine pulled a load over an iron track, 
the first real railroad. Fig. 80 shows the "Rocket" and 
two other early locomotives. 

In order to build a railroad between Liverpool and Man- 
chester for carrying both passengers and freight it was 
necessary to secure an act of Parliament. Stephenson was 
compelled to undergo a severe cross-examination by a com- 
mittee of Parliament, who feared there would be great 
danger if the speed of the trains were as high as twelve 
miles an hour. He was asked: 

''Have you seen a railroad that would stand a speed of 
twelve miles an hour?" 

"Yes." 

"Where?" 

"Any railroad that would bear going four miles an hour. 
I mean to say that if it would bear the weight at four miles 
an hour it would bear it at twelve." 

Do you mean to say that it would not require a stronger 
railway to carry the same weight at twelve miles an hour?" 

"I will give an answer to that. I dare say every person 
has been over ice when skating, or seen persons go over, 
and they know that it would bear them better at a greater 
velocity than it would if they went slower; when they go 
quickly the weight, in a measure, ceases." 

"Would not that imply that the road must be perfect?" 

"It would, and I mean to make it perfect." 

For seven miles the road must be built over a peat bog 
into which a stone would sink to unknown depths. To 
convince the committee, however, and secure the act of 
Parliament was more difficult than to build the road. But 

157 




o 
o 



bo 



NINETEENTH-CENTURY INVENTIONS 

Stephenson was one of the men who do things because they 
never give up, and the road was built. 



How a Locomotive "Works 

To understand how a locomotive works, let us consider 
how the steam is produced, how it acts on the piston, and 
how it is controlled. The steam is produced in a locomotive 
in exactly the same way that steam is produced in a tea- 
kettle. Now everybody knows that a quart of water in a 
tea-kettle with a wide bottom placed on a stove will boil 
more quickly than the same amount of water in a tea-pot 
with a narrow bottom. The greater the heating-surface — 
that is, the greater the surface of heated metal in contact 
with the water — the more quickly the water will boil and 
the more quickly steam can be produced. In a locomotive 
the aim is to use as large a heating-surface as possible. This 
is done by making the fire-box double and allowing the water 
to circulate in the space between the inner and outer parts, 
except underneath; also by placing tubes in the boiler 
through which the heated gases and smoke from the fire 
must pass. An ordinary locomotive contains two hundred 
or more of these tubes. The water surrounds these tubes, 
and is therefore in contact with a very large surface of 
heated metal. In some engines the water is in the tubes, 
and the heated gases surround the tubes. 

The steam as it enters the cylinder should be dry — that 
is, it should not contain drops of water. This is accom- 
plished by allowing the steam from the boiler to pass into 
a dome above the boiler. Here the steam, which is nearly 
11 159 



THE STORY OF GREAT INVENTIONS 

dry, enters a steam-pipe leading to the cylinder (Fig. 8i). 
The steam is admitted to the cylinder by means of a slide- 
valve. From the diagram it can easily be seen that the 
valve admits steam first on one side of the piston, then on 
the other. It can also be seen that the valve closes the 
admission-port, and so cuts off the steam before the piston 
has made a full stroke. The steam that is shut up in the 
cylinder continues to expand and act on the piston. At the 
same time the valve opens the exhaust-port, allowing the 
steam to escape from the other side of the piston; but it 
closes this port before the piston has quite finished the 
stroke. The small quantity of steam thus shut up acts like 
a cushion to prevent the piston striking the end of the 
cylinder with too great force. The exhaust-steam escapes 
through a blast-pipe into the chimney, drives the air before 
it up the chimney, and thus makes a greater draft of air 
through the fire-box. This is called the forced draft. The 
escape of the exhaust-steam causes the puffing of the loco- 
motive just after starting. After the engine is under way 
the engineer partly shuts off the steam by means of the 
reversing lever and the puffing is less noticeable. 

The action of the steam may be summed up as follows: 

1. Steam admitted to the cylinder (admission). 

2. Valve closes admission -port (cut-ofT). 

3 . Steam shut up in the cylinder expands, acting on the 
piston (expansion period). 

4. Valve opens exhaust - port to allow used steam to 
escape (exhaust). 

The devices for controlling the steam are the throttle- 
valve and the valve-gear. The throttle-valve is at the en- 

160 



a, \^ 



00 




THE STORY OF GREAT INVENTIONS 

trance to the steam-pipe in the steam-dome. This valve is 
opened and closed by means of a rod in the engineer's 
cab. 

Stephenson's link-motion valve-gear is used on most loco- 
motives. The forward rod in the diagram is in position to 
act upon the valve-rod through the lever L. Suppose the 
reversing-lever is drawn back to the dotted line ; then the for- 
ward rod will be raised and the backward rod will come into 
position to act on the lever L. If this is done while the loco- 
motive is at rest the valve is moved through one-half a com- 
plete stroke. In the diagram the steam enters the cylinder 
on the right of the piston. After this movement of the valve 
the steam would enter on the left side of the piston. In the 
present position the locomotive would move forward, but 
if the valve is changed so as to admit steam to the left of 
the piston while the connecting-rod is in the position shown 
then the engine will move backward. Thus the direction 
can be controlled by the engineer in the cab. Of course, 
this can be done while the engine is in motion. The for- 
ward rod and the backward rod are each moved by an 
eccentric on the axle of the front driving-wheel. The two 
eccentrics are in opposite positions on the axle. An eccen- 
tric acts just like a crank, causing the rod to move forward 
and backward as the axle turns, and of course this motion 
is given to the valve-rod throu2:h the lever. When the link 
is set midway between the forward and the backward rod 
the valve cannot move. When the link is raised or lowered 
part way the valve makes a short stroke, and less steam is 
admitted to the cylinder than with a full stroke. In start- 
ing the locomotive the valve is set to make a full stroke. 

162 



NINETEENTH-CENTURY INVENTIONS 

When the train is under headway the valve is set for a short 
stroke to economize steam. The valve-gear and the throttle- 
valve together take the place of the governor in the station- 
ary engine, but while the governor acts automatically these 
are controlled by the engineer. 

In reality a locomotive is two engines, one on either side, 
connected to the same driving-wheels. But the two piston- 
rods are connected to the driving-wheels at points which 
are at right angles with each other, so that when the crank 
on one side is at the end of a stroke — the * * dead centre' ' — 
that on the other side is on the quarter, either above or 
below the axle, ready for applying the greatest turning 
force. 

The expansion-engine was designed to use more of the 
power of the steam than can be done in the single-cylinder 
engine. In the double expansion-engine the steam expands 
from one cylinder into another. The second cylinder must 
be larger in diameter than the first. In the triple expansion- 
engine the steam expands from the second cylinder into a 
third, still larger. The second and third cylinders use a 
large part of the power that would be wasted with only one 
cylinder. 

The Tttfbine 

One of the great inventions relating to steam-power is 
the steam-turbine. The water-turbine is equally useful in 
relation to water-power. The water-turbine and the steam- 
turbine work in very much the same way, the difference 
being due to the fact that steam expands as it drives the 
engine, while water drives it by its weight in falling, or by 

163 



THE STORY OF GREAT INVENTIONS 



its motion as it rushes in a swift stream or jet against the 
blades of the turbine. 

The first steam-engine, that of Hero in the time of Archi- 
medes, was a form of turbine (Fig. 82). It was driven by 

the reaction of the steam as 
it escaped into the air. The 
common lawn-sprinkler, that 
whirls as the water rushes 
through it, is a water - turbine 
that works in the same way. 
"Barker's Mill" is the name 
applied to a water-turbine that 
works like the lawn-sprinkler. 
As the water rushes out of the 
opening it pushes against the 
air. It cannot push against 
the air without pushing back 
at the same time. Never y^t 
has any person or object in 
nature been able to push in 
one direction only. It can- 
not be done. If you push 
a cart forward you push backward against the ground 
at the same time. If there were nothing for you to push 
back against your forward push would not move the cart 
a hair's-breadth. If you doubt this, try to push a cart 
when you are standing on ice so slippery that you cannot 
get a foothold. It is the backward push of the water in the 
lawn-sprinkler and the backward push of the steam in 
Hero's engine that cause the machine to turn. 

164 




FIG. 82 hero's engine 



NINETEENTH-CENTURY INVENTIONS 

The turbines in common use for both water and steam 
power have curved blades. The reason for curving the 
blades can best be seen by referring to an early form of 
water-wheel. The best water-turbine is only an improved 
form of water-wheel. The first water-wheels had flat 
blades, and these answered very well so long as only a low 
power was needed and it was not necessary to save the 
power of the water. It was found, however, that there 
was a great waste of power in the wheel with flat blades. 
One inventor proposed to improve the wheel by curving the 




FIG. 83 AN UNDERSHOT WATER-WHEEL WITH CURVED BLADES 



blades in such a way that the water would glide up the 
curve and then drop directly downward (Fig. S;^). The 
water then gives up practically all of its power to the wheel 
and falls from the wheel. It would have no power to 

165 



THE STORY OF GREAT INVENTIONS 

move a second wheel. In this way he used practically 
all the power of the water. To save the power of the water 
by making all of the water strike the wheel at high speed 




FIG. 84 AN OVERSHOT WATER-WHEEL 

the channel was made narrow just above the wheel, form- 
ing a mill-race. This applies to the undershot wheel. In 
the overshot wheel (Fig. 84) the power depends on the 
weight of the water and on its height. The water runs into 
buckets attached to the wheel, and, as it falls in these 
buckets, turns the wheel. The undershot wheel and the 

166 



NINETEENTH-CENTURY INVENTIONS 



mill-race represent a common form of turbine, that form in 
which the steam or the water is forced in a jet against a 
set of curved blades. Fig. 85 shows a steam-turbine run 
by a jet of steam. In the water-turbine there are two sets 
of blades. One set rotates, the other remains fixed. The 
use of the fixed blades is to turn the water and drive it in 
the right direction against the moving blades. In some 
forms of turbine there are 
more than two sets of 
blades. The steam, as it 
passes through, gives up 
some of its power to each 
set of blades until, after 
passing the last set, it has 
given up nearly all its pow- 
er. The action of the steam 
in this turbine is somewhat 
like that in the expansion- 
engine, in which the steam 
gives up a portion of its 
power in each cylinder. 
Fig. 86 is from a photo- 
graph of a modern steam- 
turbine, and Fig. 87 is a 
drawing of the same tur- 
bine showing the course of the steam, 
that runs a large dynamo. 

In 1897, ^s the battle-ships of the British fleet were as- 
sembled to celebrate the Diamond Jubilee of Queen Victoria, 
a little vessel a hundred feet long darted in and out among 

167 




FIG. 85 DE LAVAL STEAM-TURBINE 

Driven by a jet of steam striking 
the blades. 



Fig. 88 is a turbine 



THE STORY OF GREAT INVENTIONS 

the giant ships, defied the patrol-boats whose duty it was 
to keep out intruders, and raced down the lines of battle- 
ships at the then unheard-of speed of thirty-five knots an 
hour. It was the Turhinia, fitted with the Parsons turbine. 
This event marked the beginning of the modern turbine. 




FIG. 88 A STEAM-TURBINE THAT RUNS A DYNAMO GENERATING I4,000 

ELECTRICAL HORSE-POWER 

The steam enters through the large pipe at the left. 



It also marked the beginning of a revolution in steam 
propulsion. 

The Parsons turbine does not use the jet method, but 
the steam enters near the centre of the wheel and flows 

170 



NINETEENTH-CENTURY INVENTIONS 

toward the rim, passing over a number of rows of curved 
blades. The Parsons turbine is used on the fastest ocean 
Hners. The Lusitaniay one of the fastest steamships in the 
first decade of the twentieth century, has two sets of high 
and low pressure turbines with a total of 68,000 horse-power. 

The windmill is a form of turbine driven by the air. As 
the air rushes against the blades of the windmill, it forces 
them to turn. If the windmill were turned by some me- 
chanical power, it would drive the air back, and we should 
have a blower. This is what we have in the electric fan, 
a small windmill driven by an electric motor so that it 
drives the air instead of being driven by it. The blades of 
the windmill and the electric fan are shaped very much 
like the screw propeller. The screw propeller, driven by 
an engine, would drive the water back if the ship were 
firmly anchored, just as the fan drives the air. But it can- 
not drive the water back without pushing forward on the 
ship at the same time, and this forward push propels the 
ship. It is difficult to attain what is now regarded as high 
speed with a single screw. With engines in pairs and two 
lines of shafting higher power can be used. The best 
steamers, therefore, are fitted with the twin-screw pro- 
peller. Some large steamers have three and some four 
screws. 

The screw propellers of turbine steamships are made of 
small diameter, that they may rotate at high speed without 
undue waste of power. By the use of turbine engines and 
twin-screw propellers, the weight of the machinery has been 
greatly reduced. The old paddle-wheels, with low-pressure 
engines, developed only about two horse-power for each 

171 



THE STORY OF GREAT INVENTIONS 

ton of machinery. The turbine, with the twin-screw pro- 
peller, develops from six to seven horse-power for every 
ton of machinery. The modern steamer, with all its ma- 
chinery and coal for an Atlantic voyage, weighs no more 
than the engines of the old paddle-wheel type and coal 
would weigh for the same horse-power. The steam-turbine 
and the twin-screw propeller have made rapid ocean travel 
possible. 



Chapter VI 

THE TWENTIETH-CENTURY OUTLOOK 

WE have seen that the latter half of the nineteenth cen- 
tury was a time of invention. It was a time when the 
great discoveries of many centuries bore fruit in great in- 
ventions. It was thought by some scientists that all the 
great discoveries had been made, and that all that remained 
was careful work in applying the great principles that had 
been discovered. So far was this from being true that in 
the last ten years of the nineteenth century discoveries were 
made more startling, if possible, than any that had pre- 
ceded. The nineteenth century not only brought forth 
many great inventions, but handed down to the twentieth 
century a series of discoveries that point the way to still 
greater inventions. 

Air-Ships 

For centuries men sailed over the water at the mercy of 
the wind. The sailing vessel is helpless in a storm. Early 
in the nineteenth century they learned to use the power of 
steam for ocean travel, and the wind lost its terrors. Late 
in the eighteenth century men learned to sail through the 
air in balloons even more at the mercy of the wind than the 

173 



THE STORY OF GREAT INVENTIONS 

sailing vessels on the ocean. More than a hundred years 
later they learned to propel air-ships in the teeth of the 
wind. The nineteenth century saw the mastery of the 
water. The twentieth is witnessing the mastery of the air. 

The first balloon ascension was made in 1783, two men 
being carried over Paris by what Benjamin Franklin called 
a "bag of smoke." The balloon was a bag of oiled silk 
open at the bottom. In the middle of the opening was a 
grate in w^hich bundles of fagots and sheaves of straw were 
burned. The heated air filled the balloon, and as the heated 
air was lighter than the air around it the balloon could rise 
and carry a load. Beneath the grate was a wicker car for 
the men. They were supplied with straw and fagots with 
which to feed the fire. When they wanted to rise higher 
thev added fuel to heat the air in the balloon. When they 
wished to descend they allowed the fire to die out, so that 
the air in the balloon would cool. They could not guide 
the balloon, but drifted with the wind. That great philoso- 
pher Benjamin Franklin, who saw the ascension, said that 
the time might come when the balloon could be made to 
move in a calm and guided in a w^ind. In the second 
ascension bags of sand were taken as ballast, and the car 
was suspended from a net which enclosed the balloon. In 
this second ascension hydrogen gas was used in place of 
heated air. 

The greatest height ever reached by a human being is 
about seven miles. This height was first reached in 1862 by 
two balloonist s who nearly lost their lives in the adventure. 
At a height of nearly six miles one of the men became un- 
conscious. The other tried to pull the valve-cord to allow 

174 



THE TWENTIETH-CENTURY OUTLOOK 

the gas to escape, but found that the cord was out of his 
reach. His hands were frozen, but he chmbed out of the 
car into the netting of the balloon, secured the cord in his 
teeth, returned to the car, and threw the weight of his body 
on the cord. This opened the valve and the balloon de- 
scended. 

Those who go to great heights now provide themselves 
with tanks of compressed oxygen. Then when the air 
becomes so thin and rare that breathing is difficult they 
can breathe from the oxygen tanks. 

A captive balloon in war serves as an observation tower 
from which to observe the enemy. It is connected to the 
ground by a cable. This cable is wound on a drum carried 
by the balloon wagon. The balloon can be lowered or 
raised by winding or unwinding the cable. 

(The gas-bag is sometimes made of oiled silk, sometimes 
of two layers of cotton cloth with vulcanized rubber be- 
tween. The cotton cloth gives the strength needed, and 
the rubber makes the bag gas-tight. 

The most convenient gas for filling balloons is heated air, 
but the air cools rapidly and loses its lifting power. Coal- 
gas furnished by city gas-plants is sometimes used. This 
gas will lift about thirty-five pounds for every thousand 
cubic feet. A balloon holding thirty-five thousand cubic 
feet of coal gas will easily lift the car and three persons. 
The lightest gas is hydrogen. This gas will lift about 
seventy pounds for every thousand cubic feet. Hydrogen 
is made by the action of sulphuric acid and water on iron. 
If a bit of iron is thrown into a mixture of sulphuric acid 
and water bubbles of hydrogen gas will rise through the 

12 175 



THE TWENTIETH-CENTURY OUTLOOK 

liquid. This gas will burn if a lighted match is brought 
near. 

A balloon without propelling or steering apparatus is not 
an air- ship. It may be raised by throwing out ballast or 
lowered by letting out gas, but further than this the aero- 
naut has no control over its movements. The balloon 
moves with the wind. No breeze is felt, for balloon and 
air move together. To the aeronaut the balloon seems to 
be in a dead calm. It is only when he catches sight of 
houses and trees and rivers darting past below that he 
realizes that the balloon is moving. 

If a balloon has a propelling apparatus it may move 
against the wind, or it may outspeed the wind. A balloon 
with propelling and steering apparatus is called a "dirigible" 
balloon, which means a balloon that can be guided. Figs. 
89 and 90 are from photographs of a ''dirigible" used in the 
British army. Such a balloon is usually long and pointed 
like a spindle or a cigar. It is built to cut the air, just as a 
rowboat built for speed is long and pointed so that it may 
cut the water. The propeller acts like an electric fan. An 
electric fan drives the air before it, but the air pushes back 
on the fan just as much as the fan pushes forward on the 
air, and if the fan were suspended by a long cord it would 
move backward. So the large fan or screw propeller on an 
air-ship drives the air backward, and the air reacts and 
drives the ship forward. In the same way the screw- 
propeller of an ocean liner drives the vessel forward by the 
reaction of the water. 

A balloon rises for the same reason that wood floats on 
water. The wood is lighter than w^ater, and the water 

177 



THE TWENTIETH-CENTURY OUTLOOK 

holds it up. The balloon is lighter than air and the air 
pushes it up. The upward push of the air is just equal to 
the weight of the air that would fill the same space the 
balloon fills. The balloon can support a load that makes 
the whole weight of the balloon and its load together equal 
to the weight of the air that would fill the same space. For 
the balloon to rise the load must be somewhat lighter than 
this. A balloon may be made lighter than air by filling 
it with heated air or coal-gas. Hydrogen, however, is used 
in the better balloons and in air- ships of the ''lighter than 
air" type. 

The air-ship must, of course, use a very light motor. A 
steam-engine cannot be made light enough. Neither can 
an electric motor, if we add the weight of the storage battery 
that would be required. Air-ships have been propelled by 
both steam-engines and electric motors, but with low speed 
because of the weight of the engine or motor. The only 
successful motor for this purpose is the gasolene motor, 
which is a form of gas-engine using gas formed by the 
evaporation of gasolene. 

The first air-ship that could be controlled and brought 
back to the starting-point was made in France, in 1885, by 
Captain Renard, of the French army. It was a cigar- 
shaped balloon, with a screw propeller run by an electric 
motor of eight horse-power. The ship attained a speed of 
thirteen miles an hour. 

A more successful air-ship was that built by Santos 
Dumont. With this ship, in 1901, he won a prize of $20,000, 
which had been offered to the builder of the first air-ship that 
would sail round the Eiffel Tower in Paris from the Aero- 

179 



THE STORY OF GREAT INVENTIONS 

static Park of Vaugirard, a distance of about three miles, 
and return in half an hour. 

The balloon part of this air-ship was 112 J feet long and 
19 J feet in diameter, holding about 6400 cubic feet of gas. 
The car was built of pine beams no larger in section than 
two fingers and weighing only no pounds. This car could 
be taken apart and put in a trunk. A gasolene automobile 
motor was used, and thus it is seen that the automobile 
aided in solving the problem of sailing through the air. It 
was the automobile that led to the construction of light and 
powerful gasolene motors. The car and motor were sus- 
pended from the balloon by means of piano wires, which 
at a short distance were invisible, so that the man in the 
car appeared in some mysterious way to follow the balloon. 
The ship was turned to the left or right by means of a 
rudder. It was made to ascend or descend by shifting the 
weight of a heavy rope that hung from the car, thus in- 
clining the ship upward or downward. 

Count Zeppelin, of Germany, constructed a much larger 
dirigible balloon than that of Santos Dumont. The balloon 
of the first Zeppelin air- ship w^as 390 feet in length, with a 
diameter of about 39 feet. It was divided into seventeen 
sections, each section being a balloon in itself. These sec- 
tions serve the same purpose as the water-tight compart- 
ments of a battle-ship. An accident to one section would 
not mean the destruction of the entire ship. Within the 
balloon is a framework of aluminum rods extending from 
one end to the other and held in place by aluminum rings 
twenty-four feet apart. The balloon contains about 108,000 
cubic feet of gas, and it costs about $2500 to fill it. One 

180 




FIG. 91 A ZEPPELIN AIR-SHIP 



THE STORY OF GREAT INVENTIONS 

filling of gas will last about three weeks. There are two 
cars, each about ten feet long, five feet wide, and three feet 
deep. The cars are connected by a narrow passageway 
made of aluminum wires and plates, making a walking 
distance of 326 feet — longer than the decks of many ocean 
steamers. A sliding weight of 300 kilograms (about 600 
pounds) serves the same purpose as the guide-ropes in the 
Santos Dumont air-ship. By moving this weight forward 
or backward the ship is raised or lowered at the bow or 
stern, and thus caused to glide up or down. Anchor-ropes 
are carried for use in landing. The ship is propelled by 




92 COUNT ZEPPELIN S DEUTSCHLAND, THE FIRST AIR-SHIP IN 

REGULAR PASSENGER SERVICE 

182 



THE TWENTIETH-CENTURY OUTLOOK 

four screws, and guided by a number of rudders laced 
some in front and some in the rear. The first ZeppeHn 
air-ship carried four passengers. The work of Dumont and 




Copyright by Pictorial News Co. 
FIG. 93 THE BALDWIN AIR-SHIP USED IN THE UNITED STATES ARMY 



Zeppelin has led the great powers to manufacture dirigible 
balloons for use in time of war. Fig. 91 shows one of the 
Zeppelin air-ships sailing over a lake. 

A larger air-ship, the Deutschland, built later by Count 
Zeppelin, was the first air-ship to be used for regular pas- 
senger service. The Deutschland is shown in Fig. 92. The 
Deutschland carried the crew and twenty passengers. It 

183 



THE STORY OF GREAT INVENTIONS 

operated for a time as a regular passenger air-ship between 
Friedrichshafen and Diisseldorf , a distance of three hundred 
miles. The Deutschland was wrecked in a storm on June 28, 
19 10, but it was successfully operated long enough to give 
Germany the honor of establishing the first air-ship line for 
regular passenger service. This is an honor perhaps equal- 
ly as great as that of establishing the first commercial elec- 
tric railway, which also belongs to Germany. An American 
army air-ship is shown in Fig. 93. 

The Aeroplane 

(The aeroplane is a later development than the dirigible 
balloon. The aeroplane is heavier than air. So is a bird 
and so is a kite. What supports a kite or a bird as it soars ? 
Every boy knows that the strings of a kite must be attached 
so that the kite is inclined and catches the wind under- 
neath. Then the wind lifts the, kite. In still air the kite 
will not fly unless .the boy who holds the string runs very 
fast and so causes an artificial breeze to blow against the 
kite. In much the same way a hovering bird is held aloft 
by the wind. In a dead calm the bird must flap its wings 
to keep afloat. If the kite string is cut the kite tips over 
and drops to the earth because it has lost its balance. The 
lifting power of the wind is well shown in the man-lifting 
kites which are used in the British army service. In a high 
wind a large kite is used in place of a captive balloon. It 
is a box -kite made of bamboo and carries a passenger in a 
car, the car running on the cable which attaches the kite 
to the ground. Now suppose a kite with a motor and pro- 

184 





FIG. 94 — IN FULL FLIGHT 



THE STORY OF GREAT INVENTIONS 

peller in place of a string and a boy to run with it, and that 
the kite is able to balance itself, then it will sail against a 
wind of its own making and you have a flying-machine 
heavier than air. 

The first aeroplane that would fly under perfect control 
of the operator was built by the Wright brothers at Dayton, 
Ohio. When they were boys, Bishop Wright gave his two 
sons, Orville and Wilbur, a toy flyer. Prom that time on 
the thought of flying through the air was in their minds. 
A few years later the death of Lilienthal, who was killed by 
a fall with his glider in Germany, stirred them, and they 
took up the problem in earnest. They read all the writings 
of Lilienthal and became acquainted with Mr. Octave 
Chanute, an engineer of Chicago who had made a success- 
ful glider. They soon built a glider of their own, and ex- 
perimented with it each summer on the huge sand-dunes of 
the North Carolina coast. 

A glider is an aeroplane without a propeller. With it 
one can cast off into the air from a great height and sail 
slowly to the ground. Before attempting to use a motor 
and propeller, the Wrights learned to control the glider 
perfectly. They had to learn how to prevent its being 
tipped over by the wind, and how to steer it in any direc- 
tion. This took years of patient work. But the problem 
was conquered at last, and they attached a motor and pro- 
peller to the glider, and had an air-ship under perfect con- 
trol and with the speed of an express- train. Their flyer 
of 1905, which made a flight of twenty-four miles at a speed 
of more than thirty-eight miles an hour, carried a twenty- 
five-horse-power gasolene motor, and weighed, with its load, 

186 






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THE STORY OF GREAT INVENTIONS 

925 pounds. Figs. 94 and 95 show the Wright air-ship in 
flight. Fig. 97 shows the mechanism. 

How the Wright Aeroplane Is Kept Afloat 

The Wright aeroplane is balanced by a warping or twist- 
ing of the planes i and 2, which form the supporting sur- 
faces (Fig. 96) . If left to itself the machine would tip over 
like a kite when the string is cut and drop edgewise to 
the ground. Suppose the side R starts to fall. The cor- 
ners a and e are raised by the operator while b and / are 
lowered, thus twisting the planes, as shown in the dotted 
lines of the figure. The side R then catches more wind than 
the side L. The wind exerts a greater lifting force on R than 
on L, and the balance is restored. The twist is then taken 
out of the machine by the operator. A ship when sailing 
on an even keel presents true unwarped planes to the wind. 

The twisting is brought about by a pull on the rope 3, 
which is attached at d and c, and passes through pulleys at 
g and h. When the rope is pulled toward the left the right 
end is tightened and slack is paid out at the left end. This 
pulls down the corner d, and raises e. The corner a is 
raised by the post which connects a and e. The rope 4, 
passing from a to 6 through pulleys at m and n, is thus 
drawn toward a and pulls down the corner b. Thus a is 
raised and b is lowered. At the same time rope 4 turns 
the rear rudder to the left, as shown by the dotted lines, 
thus forcing the side R against the wind. Of course, if 
the left side of the machine starts to fall, the rope 3 is 
pulled toward the right, and all the movements take place 



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THE STORY OF GREAT INVENTIONS 

in the opposite direction. The ropes are connected to a 
lever, by which the operator controls the warping of the 
planes. These movements are possible because the joints 
are all universal, permitting movement in any direction. 
In whatever position the planes may be set, they are held 
perfectly rigid by the two ropes, together with others not 
shown in the figure. The machine is guided up or down 
by the front horizontal rudder. 

When the aeroplane swings round a curve the outer wing 
is raised because it moves faster than the inner wing, and 
therefore has greater lifting force. Thus the aeroplane banks 
its own curves. 

The Wright flying-machine is called a biplane because it 
has two principal planes, one above the other. A number of 
successful flying-machines have been built with only one 
plane, and these are called monoplanes. A monoplane that 
early became famous is that of Bleriot (Fig: 98). The 
Bleriot monoplane was the first flying-machine to cross the 
English Channel. This machine is controlled by a single 
lever mounted with a ball-and-socket coupling, so that it 
can move in any direction. When on the ground it is sup- 
ported by three wheels like bicycle wheels, so that it does 
not require a track for starting, but can start anywhere from 
level ground. The Wright and the Bleriot represent the 
two leading types of early successful flying-machines. 

Sttbmarines 

Successful navigation beneath the surface of the water, 
though not carried to the extent im.agined by Jules Verne, 

190 



THE STORY OF GREAT INVENTIONS 

was a reality at the beginning of the twentieth century, 
(instead of twenty thousand leagues under the sea, less 
than a hundred leagues had been accomplished^ but no one 
can foretell what the future may have in store. 

The principal use of the submarine is in war. It is a 
diving torpedo - boat, and acts under cover of water|( as 




Copyright by M. Brauger, Paris 
FIG. 98 THE BLERIOT MONOPLANE 

the light artillery on land is secured behind intrenchments} 
The weapon used by the submarine is the torpedo. The 
torpedo is itself a small submarine able to propel itself, and 
if started in the water toward a certain object, to go under 
water straight to the mark. It carries a heavy charge either 

192 



THE TWENTIETH-CENTURY OUTLOOK 

of guncotton or dynamite, which explodes when the tor- 
pedo strikes a soHd object, such as a battle-ship. The first 
torpedo was intended to be steered from the shore by means 
of long tiller-ropes, and to be propelled by a steam-engine 
or by clockwork. The Whitehead fish torpedo, invented 
in 1866, is self- steering. At the head of the torpedo is a 
pointed steel firing-pin. When the torpedo strikes a ship 
or any rigid object this steel pin is driven against a det- 
onator cap which is in the centre of the charge of dyna- 
mite. The blow causes the cap to explode, and the ex- 
plosion of the cap explodes the dynamite. The torpedo is 
so arranged that it cannot explode until it is about thirty 
yards away from the ship from which it is fired. The steel 
pin cannot strike the cap until a small "collar" has been 
revolved off by a propeller fan, and this requires a distance 
of about thirty yards. The screw propeller is driven by 
compressed air. A valve which is worked by the pressure 
of the water keeps the torpedo at any depth for which the 
valve is set. The torpedo contains many ingenious devices 
for bringing it quickly to the required depth and keeping 
it straight in its course. One of these devices is the gyro- 
scope, which will be described under the head of "spinning 
tops." Whitehead torpedoes are capable of running at a 
speed of over thirty-seven miles an hour for a range of two 
thousand yards and hitting the mark aimed at almost as 
accurately as a gun. The submarine boat carries a number 
of torpedoes, and has one torpedo-tube near the forward 
end from which to fire the torpedoes.; 

It would be very difficult for one submarine to fight an- 
other submarine, for the submarine when completely sub- 

193 



THE STORY OF GREAT INVENTIONS 

merged is blind. It could not see in the water to find its 
enemy. \The torpedo-boat-destroyer is able to destroy a 
submarine by means of torpedoes, shells full of high ex- 
plosives, or quick-firing guns. Advantage must be. taken 
of the moment when the submarine comes to the surface 
to get a view of her enemy.' 

One of the great enemies of the submarine will probably 
be the air- ship, for while the submarine when under water 
cannot be seen from a ship on the surface, it can, under 
favorable conditions, be seen from a certain height in the 
air. 

Most submarines use a gasolene motor for surface travel, 
and an electric motor run by a storage battery for naviga- 
tion below the surface. The best submarines can travel at 
the surface like an ordinary boat, or "awash " — that is, just 
below the surface — with only the conning tower projecting 
above the water, or they can travel completely submerged. 

The rising and sinking of the submarine depend on the 
principle of Archimedes. The upward push of the water is 
just equal to the weight of the water displaced. If the 
water displaced weighs more than the boat, then the up- 
ward push of the water is greater than the weight of the 
boat and the boat rises. However, the boat can be made 
to dive when its weight is just a little less than the weight 
of the water displaced. This is done by means of horizon- 
tal rudders which may be inclined so as to cause the boat 
to glide downward as its propeller drives it forward. 

The magnetic compass is not reliable in a submarine with 
a hull made of steel. The electric motor used for propel- 
ling the boat under water also interferes with the action of 

194 



THE TWENTIETH-CENTURY OUTLOOK 

the compass, because of its magnetic field. The gyroscope, 
which we shall describe later, is not affected by magnetic 
action, and may take the place of the compass. 

Water ballast is used, and when the submarine wishes to 
dive, water is admitted into the tanks until the boat is 
nearly heavy enough to sink of its own weight. It is then 
guided downward by the horizontal rudder. The sub- 
marine is driven by a screw propeller, and some submarines 
are lowered by means of a vertical screw. Just as a hori- 
zontal screw propels a vessel forward, so a vertical screw 
will propel it downward. When the submarine wishes to 
rise, it may do so by the action of its rudder, or the water 
may be pumped out of its tanks, when the water will raise 




FIG. 99 THE 'PLUNGER 

Photo by Pictorial News Co. 



THE STORY OF GREAT INVENTIONS 

it rapidly. A submarine which is kept always a little 
lighter than water will rise to the surface in case of accident 
to its machinery. Figs. 99, 100, and 10 1 are from photo- 
graphs of United States submarines. 

There is one kind of submarine built for peaceful pur- 
suits which deserves mention. It is the Argonaut, invented 
by Simon Lake. This remarkable boat crawls along the 
bottom of the sea, but not at a very great depth. It is 
equipped with divers' appliances, and is used in saving 
wreckage. Divers can go out through the bottom of the 
boat, walk about on the sea bottom, and when through with 
their work re-enter the boat; all the while boat and men 
are, perhaps, a hundred feet below the surface. The divers' 
compartment, from which the divers go out into the water, 
is separated by an air-tight partition from the rest of the 
boat. Compressed air is forced into this compartment until 
the pressure of the air equals the pressure of the water out- 
side. Then the door in the bottom is opened, and the air 
keeps the water out. The men in their diving-suits can 
then go out and in as they please. 

For every boat there is a depth beyond which it must 
not go. The penalty for going beyond this depth is a 
battered-in vessel, for the pressure increases with the depth. 
Every time the depth is increased thirty-two feet the press- 
ure is increased fifteen pounds on every square inch. Be- 
yond a certain depth the vessel cannot resist the pressure. 
Submarines have been made strong enough to withstand 
the pressure at a depth of five thousand feet, or nearly a 
mile. Most submarines, however, cannot go deeper than 
a hundred and fifty feet. 

196 



THE STORY OF GREAT INVENTIONS 

Air is supplied to the occupants of the boat either from 
reservoirs containing compressed air or oxygen, or by means 
of chemicals which absorb the carbon dioxide produced in 
breathing and restore the needed quantity of oxygen to the 
air. 

While the men in the boat cannot see in the water, they 
can see objects on the surface of the water, even when their 




FIG. lOI FIRST SUBMARINE CONSTRUCTED IN UNITED STATES. IT WENT 

TO THE BOTTOM WITH SEVEN' MEN, WHO WERE DROWNED 
Photo by Pictorial News Co. 



boat is several feet below the surface, by means of the peri- 
scope. This is an arrangement of lenses and mirrors in a 
tube bent in two right angles, which projects a short dis- 
tance above the surface and can be turned in any direction 

198 



THE TWENTIETH-CENTURY OUTLOOK 



(Fig. 102). Thus the boat, 
while itself nearly invisible, 
can have a clear view of the 
battle-ship w^hich it is about 
to attack. 

Some Spinning Tops that 
Are Useful 

Every one knows that a 
top will stand upright only 
when it is spinning. Most 
tops when spinning will 
stand very rough treatment 
without being upset. The 
whip -top will stand a se- 
vere lashing. Spin a top 
upright and give it a knock. 
It will go round in a circle 
in a slanting position, and 
after a time will right itself. 
If the top is struck toward 
the south it will not bow 
toward the sputh, but tow^- 
ard the east or w^est. In 
throwing a quoit, the quoit 

must be given a spinning motion or the thrower cannot be cer- 
tain how it will alight. A coin thrown up with a spinning mo- 
tion will not turn over. The quoit and the coin are like the 
top. They will not turn over easily when spinning. For 
the same reason a rifle bullet is set spinning by the spiral 

199 




FIG. 102 HOW MEN IN A SUBMARINE 

SEE WHEN UNDER THE WATER 



THE STORY OF GREAT INVENTIONS 

grooves in the bore of the gun, and it goes straight to its 
mark. With a smooth-bore gun that does not set the bullet 
spinning the gunner cannot be sure of his aim. 

It took a long time to discover that the spinning top is 
a useful machine. It is useful because of its steady motion, 
because it is difficult to turn over. It was discovered by 
Newton long ago that every moving object tries to keep 
on in the direction in which it is moving. A moving object 
always requires some force to change its direction. The 
spinning top is a beautiful illustration of this principle. 
The top that is most useful is the gyroscope top (Fig. 103). 
It is mounted on pivots so arranged that the top can turn in 
any direction within the frame that supports it. If the 
top is set spinning one may turn the frame in any direction, 




FIG. 103 A TOP THAT SPINS ON A STRING 

but the top does not change direction. The axis of the top 
will point in the same direction all the while the top is 
spinning, no matter how the supporting frame is moved 
about. The top will spin on a string. If attached inside 

209 



THE TA?7ENTIETH-CENTURY OUTLOOK 

a box the box can be made to stand on one corner while the 
top is spinning. 

This top, which is so hard to upset, has been used in ships 
to prevent the ship being rolled by the waves. A large fly- 
wheel is mounted in the middle of the vessel on a hori- 
zontal axle. A fly-wheel is only a large top. It spins with 
a steady motion, and because of its larger size it is very 
much harder to overturn than a toy top. The fly-wheel in 
the ship resists the rolling force of the waves and steadies 
the ship, so that even with high waves the rolling can 
scarcely be felt. The waves do not so readily break over 
the ship when thus steadied by the revolving wheel. 

The gyroscope is also used in some forms of torpedo to 
give the torpedo steady motion. By means of a spring re- 
leased by a trigger the gyroscope within the torpedo is set 
spinning before the torpedo enters the water. The gyro- 
scope keeps its direction unchanged, and as the torpedo 
turns one way or the other the gyroscope acts upon one or 
the other of two valves connected with the compressed-air 
chambers from which the screws of the torpedo are driven. 
The air thus set free by the gyroscope drives a piston-rod 
connected with a rudder in such a way as to right the tor- 
pedo. The torpedo goes through the water with a slightly 
zigzag motion, but never more than two feet out of the line 
in which it was aimed. 

The Monorail-Car 

Another use of the gyroscope is in the monorail-car. To 
make a car run on a single rail, with its weight above the 

201 



THE STORY OF GREAT INVENTIONS 



rail, was impossible until the use of the gyroscope was dis- 
covered. In the monorail-car invented by Brennan (Fig. 
104) there are two gyroscopes, each weighing fifteen hun- 
dred pounds, driven at a speed of three thousand revolu- 
tions a minute by an electric motor. Each gyroscope wheel 




FIG. 104 A CAR THAT RUNS ON ONE RAIL 

Louis Brennan's full-size monorail. 



with its motor is mounted in an air-tight casing from which 
the air is pumped out. The wheel will run much more easily 
in a vacuum than in air, for the air offers very great resist- 
ance to its motion. The wheels are placed one on each side 
of the car with their axles horizontal. When the car starts 
to fall the spinning gyroscopes right it much as a spinning 
top rights itself if tipped to one side by a blow. If the wind 
tips the car to the left the gyroscopes incline to the right 



202 



THE TWENTIETH-CENTURY OUTLOOK 

until the car is again upright. If the load is heavier on the 
right side the car inclines itself toward the left just as a 
man leans to the left when carrying a load on his right 
shoulder. In rounding a curve the car leans to the inside 
of the curve just as a bicycle rider does, and as a railway 
train is made to do by laying the outer rail of the curve 
higher than the inner rail. Two gyroscopes spinning in 
opposite directions are necessary to keep the car from fall- 
ing when rounding a curve. 

The gyroscope may be used in place of a compass. If it 
is set spinning in a north and south direction it will con- 
tinue to spin in a north and south direction, no matter how 
the ship may turn. It is even more reliable than the com- 
pass, for it is not affected by magnetic action. Possibly 
some of the great inventions yet to be made will be new 
uses of the spinning top. 

Liquid Air and the Greatest Cold 

For a long time after men had learned the use of the fur- 
nace and could produce great heat, the greatest cold known 
w^as that of the mountain -top. Men wondered what would 
happen if air could be made colder than the frost of winter, 
but knew not how to bring about such a result. They won- 
dered what things could be frozen that remain liquid or 
gaseous even in the cold of winter. 

The first artificial cold was produced by a mixture of 
salt and ice, such as we now use in an ice-cream freezer. 
In time men learned other ways of producing great cold 
and even to manufacture ice in large quantities. 

203 



THE STORY OF GREAT INVENTIONS 

The cold of liquid air is far greater than that of ice or 
even a freezing mixture of salt and ice. Liquid air is simply 
air that is so cold that it becomes a liquid just as steam 
when cooled forms water. Steam has only to be cooled to 
the temperature of boiling water, while air must be cooled 
to 314 degrees below zero on the Fahrenheit scale. 

If it were possible for us to live in such a climate, and 
the world were cooled to the temperature of liquid air, we 
should have a curious world. Watch - springs might be 
made out of pewter, bells of tin, and piano wires of solder, 
for these metals are made stronger by the extreme cold of 
liquid air. There would be no air to breathe. Oceans and 
rivers would be frozen solid, and the air would form a liquid 
ocean about thirty-five feet deep. This ocean of liquid air 
would be kept boiling a long time by the heat of the ice 
beneath it, for ice is hot compared with liquid air. The ice 
would cool as it gave up its heat to the liquid air and in 
time become as cold as the liquid air itself. 

Liquid air has been shipped thousands of miles in a double 
walled tin can, the space between the two walls being filled 
with felt. The felt protects the liquid air from the heat of 
the air without. The liquid air evaporates slowly, and es- 
capes through a small opening at the top. 

Professor Dewar, a successor of Faraday in the Royal 
Institution, invented the Dewar bulb, by means of which 
the evaporation of the liquid air is prevented. This bulb 
is a double-walled flask. In the space between the two 
walls of the flask is a vacuum. Now a vacuum is the best 
possible protection against heat. If we were to take a 
bottle full of air and pump out from the bottle all except 

204 



THE TWENTIETH-CENTURY OUTLOOK 

about a thousandth of a milHonth of the air it contained at 
first we should have such a vacuum as that of the Dewar 
bulb. With such a vacuum around it ice could be kept 
from melting for many days even in the hottest weather, 
for no heat can go through a vacuum. 

But the greatest cold is not the cold of liquid air. Liquid 
hydrogen is so cold that it freezes air. When a flask of 
liquid hydrogen is opened there is a small snow-storm of 
frozen air in the mouth of the flask. But even this is not 
the greatest cold. The liquid hydrogen may be frozen, 
forming a hydrogen snow whose temperature is 43 5 degrees 
below zero. This is nearly equal to the cold of the space 
beyond the earth's atmosphere, which is the greatest pos- 
sible cold. 

The Electric Ftirnace and the Greatest Heat 

The greatest heat that has yet been produced artificially 
is that of the electric arc. The exact temperature of the 
electric arc is not known with certainty. It is known, how- 
ever, that the temperature of the hottest part of the arc 
is not less than 6500 degrees Fahrenheit. When we com- 
pare this with the temperature of the hottest coal furnace, 
which is about 4000 degrees, we can very easily understand 
that something is likely to happen at the temperature of 
the electric arc that could not happen in an ordinary 
furnace. 

If an electric arc is enclosed by something that will hold 
the heat in we have an electric furnace, and any substance 
placed in the furnace may be made nearly as hot as the 

205 



THE STORY OF GREAT INVENTIONS 

arc itself. In the electric furnace any substance, whether 
found in nature or prepared artificially, may be melted or 
vaporized. 

It was Henri Moissan, Professor of Chemistry at the Sor- 
bonne in Paris, who made the first great discoveries in the 
use of the electric furnace and produced the first artifi- 
cial diamonds. The study of diamonds led Moissan to be- 
lieve that in nature they are formed by the cooling of a 
melted mixture of iron and carbon. He could prepare such 
a mixture with his electric furnace, he thought, and so 
make diamonds like those of the diamond mines. So, with 
an electric furnace having electrodes as large as a man's 
wrist, a mixture of iron and charcoal in a carbon crucible, 
and a glass tank filled with water, Moissan set out to change 
the charcoal to diamonds. At a temperature of more than 
six thousand degrees the iron and charcoal were melted to- 
gether. For a time of from three to six minutes the mixture 
was in the intense heat. Then the covering of the furnace 
was removed and the crucible with the melted mixture 
dropped into the tank of water. With some fear this was 
done for the first time, for it was not known what would 
happen when such a hot object was dropped into cold 
water. But no explosion occurred, only a violent boiling 
of the water, a fierce blazing of the molten mass, and then 
a gradual change of color from white to red and red to 
black. With boiling acids and other chemicals the refuse 
was removed, and the fragments that remained were found 
to be diamonds, small, it is true, so small that they could 
be seen only with the aid of a microscope, but giving prom- 
ise of greater things to come. The outer crust of iron held 

206 




FIG. 105 MANUFACTURING DIAMONDS FIRST OPERATION 

Preparing the furnace. Charcoal and iron ore placed in a crucible and 
subjected to enormous heat electrically. 



THE STORY OF GREAT INVENTIONS 

the melted charcoal under enormous pressure while it 
slowly cooled and formed the diamond crystals. The proc- 
ess of manufacturing diamonds is illustrated in Figs. 105, 
106, and 107. 

The electric furnace has made possible the preparation 
of substances unknown before, and the production in large 
quantities at low cost of substances that before were too 
costly for general use. One of the best known of these 
substances is aluminum. With the discovery of the electric- 
furnace method of extracting aluminum from its ores, the 
price of aluminum fell from one hundred and twenty-four 
dollars per pound to twelve cents per pound. 

Among the many uses of the electric furnace we may 
mention the preparation of calcium carbide, which is used 
in producing the acetylene light; carborundum, a sub- 
stance almost as hard as diamond; and phosphorus, which 
is used in making the phosphorus match. It is used also 
to some extent in the manufacture of glass, and, in some 
cases, for extracting iron from its ores. 

The Wireless Telegraph 

A ship in a fog is struck by another ship. The water 
rushes in, puts out the fires in the boilers, the engines stop, 
the ship is helpless in mid-ocean in the darkness of the night. 
But the snapping of an electric spark is heard in one of the 
cabins. Soon another vessel steams alongside. The life- 
boats are lowered and every person is saved. The call for 
help had gone out over the sea in every direction for two 
hundred miles. Another ship had caught the signal and 

208 




FIG. I06 MANUFACTURING DIAMONDS SECOND OPERATION 

The furnace at work. 



THE STORY OF GREAT INVENTIONS 

hastened to the rescue, and the world reahzed that the 
wireless telegraph had robbed the sea of its terrors. 

Without the curious combination of magnets, wires, and 
batteries on the first ship no signal could have been sent, 
and without such a combination on the second ship the 
signal would have passed unheeded. How was this com- 
bination discovered, and how does it work? 

Faraday, as we have seen, discovered the principle of the 
induction-coil. With the induction-coil a powerful electric 
spark can be produced. The friction electrical machine was 
known long before the time of Faraday. Franklin proved 
that a stroke of lightning is like a spark from an electrical 
machine, only more powerful. These great discoverers did 
not know, however, that an electric spark sends out some- 
thing like light which travels in all directions. They did 
not know it, because they had no eyes to see this strange 
light. 

I will tell you a fable to make the meaning clear. There 
once lived a race of blind men. Not one of them could see. 
They built houses and cities, railroads and steamships, 
but they did everything by touch and sound. When they 
met they touched each other and spoke, and each man 
knew his friend by the sound of his voice. One day a wise 
man among them said he believed there was something 
besides the sound of the voice with which they could make 
signals to each other. Another wise man thought upon 
this matter for some time and brought forth a proof that 
there is something called light, though no man could see it. 
Another, wiser and more practical, invented an eye which 
any man could carry about with him and see the light 

210 




riQ^ 107 MANUFACTURING DIAMONDS THIRD OPERATION 

Plunging the crucible into cold water. Observe the white-hot carbon 
just removed from the furnace. 



THE STORY OF GREAT INVENTIONS 

when he turned it in the direction from which the Hght 
was coming. Thereafter each man carried a hght that 
flashed hke the flashing of a firefly. Each man also carried 
an eye, and each could see his friend as well as hear the 
sound of his voice. 

The fable is true. The light which no man had seen we 
now call electric waves. The eye with which any one can 
perceive this light is the receiving instrument of the wire- 
less telegraph. The strange light flashed out whenever an 
electric spark passed from an electrical machine, a Leyden 
jar, an induction-coil, or as lightning in the clouds, but for 
hundreds of years this light was unseen. The human eye 
could not see it, and no artificial eye that would catch elec- 
tric waves had been invented. A man in England, James 
Clerk-Maxwell, first proved that there is such a light. Hein- 
rich Hertz, a German, first made an eye that would catch 
the waves from the electric spark, and the man who first 
perfected an eye with which one could catch the electric 
waves at a great distance and improved the instruments 
for sending out such waves was Marconi. 

The fable is true, for electric waves are like the light from 
the sun. They go through space in all directions as light 
does. They will not merely go through air, but through 
what we call empty space, or a vacuum, as light will. If we 
think of waves somewhat like water waves, but not exactly 
like them, rushing through space, we have about as good a 
picture of electric waves as we can well form in our minds. 
As the light of a lamp goes out in all directions, so do the 
electric waves go out in all directions from the place where 
the electric spark passes. Since these waves go through 

212 



THE TWENTIETH-CENTURY OUTLOOK 

what we call empty space, we must think of something in 
that space and that it is not really empty. Examine an in- 
candescent electric lamp. The bulb was full of air when 
the carbon thread was placed in it. The air was then 
pumped out until only about a millionth part remained. 
The bulb was then sealed at the tip and made air-tight. 
We say the space inside is a vacuum. If the bulb is broken 
there is a loud report as the air rushes in. Is the bulb really 
empty after the air is pumped out ? Is anything left in the 
bulb around the carbon thread? Turn on the electric cur- 
rent and the carbon thread becomes white hot. The light 
from the white-hot carbon thread goes out through the 
vacuum. There is nothing in the vacuum that we can see 
or feel or handle, but something must be there to carry the 
light from the carbon thread. The light of the sun comes 
to the earth through ninety-three million miles of space. 
Is there anything between the earth and the sun through 
which this light can pass? Light, we know, is made up of 
waves, and we cannot think of waves going through empty 
space. There must be something between the sun and the 
earth. That something through which the light of the sun 
comes to the earth we call the ether. It is the ether that 
carries the light across the vacuum in the light bulb as well 
as from the sun to the earth. Electric waves used in wire- 
less telegraphy go through this same ether. The light of 
the sun is made up of the same kind of waves, and we do 
not think it strange because it is so common. It is true 
we do not see light waves, but they affect our eyes so that 
by means of them we can see objects and perceive the flash- 
ing of a light. So with the wireless receiving instrument we 

213 



THE STORY OF GREAT INVENTIONS 

do not see the electric waves, but we perceive the flashing 
of the strange light. Electric waves and light travel with 
the same speed — 186,000 miles in a second. A wireless 
message will go around the earth in about one-seventh of 
a second. 

Electric waves will go through a brick wall as readily as 
sunlight will go through a glass window, but that is not so 
strange as it may seem. Red light will not go through blue 
glass. Blue glass holds back the red light, but lets the 
blue light go through. So the brick wall holds back com- 
mon light, but allows the light which we call electric waves 
to go through. 

Some waves on water are longer than others. So electric 
waves are longer than light waves. That is the only differ- 
ence between them. In fact, the light of the sun is made 
up of very short electric waves. These short waves affect 
our eyes, but the longer electric waves do not. We are daily 
receiving the wireless-telegraph waves from the sun, which 
we call light. Electric waves used in wireless telegraphy 
vary from about six hundred feet to two miles in length, 
while the longest light waves that affect our eyes are only 
one thirty-three-thousandth of an inch in length. 

The sensitive part of the Marconi receiving apparatus is 
the coherer. The first coherer was made in 1890 by Prof. 
Edward Branly, of the Catholic University of Paris. Very 
fine metal filings were enclosed in a tube of ebonite and 
connected in a circuit with a battery and a galvanometer. 
The filings have so high a resistance that no current flows. 
The waves from an electric spark, however, affect the filings 
so that they allow the current to flow. The electric waves 

214 



THE TWENTIETH-CENTURY OUTLOOK 

are said to cause the filings to cohere — that is, to cHng to- 
gether more closely. It is a peculiar form of electric weld- 
ing. Branly discovered that a slight tapping of the tube 
loosens the filings and stops the flow of the current. 

All that was needed for wireless telegraphy was at hand. 
Men knew how to produce electric waves of any desired 
length. They knew how they would act. A sensitive re- 
ceiver had been discovered. There was needed the prac- 
tical man who should combine the parts, improve details, 
and apply the wireless telegraph to actual use. This was 
the work of Guglielmo Marconi. In 1894, at the age of 
twenty, Marconi began his experiments on his father's 
estate, the Villa Grifone, Bologna, Italy. Fig. 108 is from a 
photograph of Marconi and his wireless sending and receiv- 
ing instruments. 




FIG. 108 MARCONI AND HIS WIRELESS-TELEGRAPH SENDING AND 

RECEIVING INSTRUMENTS 



THE STORY OF GREAT INVENTIONS 

To Marconi, telegraphing through space without wires 
appears no more wonderful than telegraphing with wires. 
In the wire telegraph electric waves, which we then call an 
electric current, follow a wire somewhat as the sound of the 
voice goes through a speaking-tube. In the wireless telegraph 
the electric waves go out through space without any wire 
to guide them. The light and heat waves of the sun travei 
to us through millions of miles of space without requiring any 
conducting wire. That electric waves should go though 
space in the same way that light does is no more wonderful 
than that the waves should follow all the turns of a wire. 

The sending instrument used by Marconi includes an in- 
duction-coil, one side of the spark-gap being connected to 
the earth and the other to a vertical wire (Fig. 109). There 
must be a battery of Leyden jars in the circuit of the sec- 
ondary coil. The induction-coil may be operated by a 
storage battery or dynamo. The vertical wire, or antenna, 
is to the sending instrument what the sounding-board is to 
a violin. It is needed to increase the strength of the waves. 
In the wireless telegraph some wires must be used. It 
is called wireless because the stations are not connected 
by wires. The antenna for long-distance work consists of 
a network of overhead wires. When the key is pressed a 
rapid succession of sparks passes across the spark-gap. The 
antenna, or overhead wire, is thus made to send out electric 
waves. By pressing the key for a longer or shorter time, a 
longer or shorter series of waves may be produced and a 
correspondingly longer or shorter effect on the receiver. In 
this manner the dots and dashes of the Morse alphabet may 
be transmitted. 

216 



THE TWENTIETH-CENTURY OUTLOOK 



o a 



<lnduciLon-coil 



Edri/? 



FIG. 109 DIAGRAM OP WIRELESS-TELEGRAPH SENDING APPARATUS 

At the receiving station there are two circuits. One in- 
cludes a coherer, a local battery, and a telegraph relay (Fig. 
no). The other circuit, which is opened and closed by the 
relay, includes a recording instrument and a tapper. One 
end of the coherer is connected to the earth and the other 
to a vertical wire like that used for the transmitter. The 



217 



THE STORY OF GREAT INVENTIONS 

electric waves weld the filings in the coherer, and this closes 
the first circuit. The relay then closes the second circuit, 
the recording instrument records a dot or a dash, and the 
tapper strikes the coherer and breaks the filings apart ready 
for another stream of electric waves. 



Coherer 



K) 



Bell 



Battery 



£arih 



FIG. 110 DIAGRAM OF MARCONI WIRELESS-TELEGRAPH RECEIVING 

APPARATUS 

The second circuit described in the text is not shown here. The relay 
and the second circuit would take the place of the electric bell. In the 
circuit as shown here the electric waves would cause the coherer to close 
the circuit and ring the bell. 

2l8 



THE TWENTIETH-CENTURY OUTLOOK 

With this arrangement it was possible to work only two 
stations at one time. Though stations were to be estab- 
lished in all the cities of Great Britain, only one message 
could be sent at one time, and all stations but one niust 
keep silence, because a second series of weaves w^ould mingle 
with the first and confusion would result. 

Marconi's next effort was ■:o make it possible to send any 
number of messages at one time. This led to his system of 
tuning the sending and receiving instruments. With this 
system the receiving instrument will take a message only 
from a sending instrument with which it is in tune. It is 
possible, therefore, for any number of wireless - telegraph 
stations to operate at the same time, the waves crossing 
one another in all directions without interfering, each 
receiver responding to the waves intended for it. An 
ocean steamer can, with the tuned system, send one mes- 
sage and receive another from a different station at the 
same time. 

Marconi's ambition was to send a wireless message across 
the Atlantic. Quietly he made his preparation, building at 
Poldhu, Cornwall, England, a more powerful transmitter 
than had yet been used. At noon on the 12th of December, 
1901, he sat in a room of the old barracks on Signal Hill, 
near St. Johns, Newfoundland, waiting for a signal from 
England. His assistants at the Poldhu station were to 
telegraph across the ocean the letter ' ' S " at certain times 
each day. Gn the table was the receiving apparatus, made 
very sensitive, and including a telephone receiver. A wire 
led out of the window to a huge kite, which the furious wind 
held four hundred feet above him. One kite and a balloon 

219 



THE STORY OF GREAT INVENTIONS 

used for supporting the antenna had been carried out to 
sea. He held the telephone receiver to his ear for some 
time. The critical time had come for which he had worked 
for years, for which his three hundred patents had prepared 
the way, and for which his company had erected the costly 
power station at Poldhu. Calmly he listened, his face 
showing no sign of emotion. Suddenly there sounded the 
sharp click of the tapper as it struck the coherer. After a 
short time Marconi handed the telephone receiver to his 
assistant. ''See if you can hear anything," he said. A 
moment later, faintly and yet distinctly, came the three 
little clicks, the dots of the letter '*S" tapped out 
an instant before in England. Marconi's victory was 
won. 

A flying-machine can de equipped with a wireless-tele- 
graph outfit, so that a man can telegraph while flying 
through the air. Two men are needed, one to operate the 
flying-machine, the other to send the telegraphic messages. 
This has been done with the Wright machine and with some 
dirigible balloons. Of course, the wireless instruments on 
the flying-machine cannot be connected to the ground. In- 
stead of the ground connection there is a second antenna, — 
one antenna on each side of the spark-gap. While in the 
ordinary wireless instruments the discharge surges back 
and forth between the antenna and the earth, in the flying- 
machine wireless the discharge surges back and forth be- 
tween the two antennae. In the Wright machine, when 
equipped for wireless telegraphy, the two antennas are 
placed one under the upper plane, the other under the lower 
plane of the flying-machine. 

?20 



THE TWENTIETH-CENTURY OUTLOOK 

More power is required for the wireless than for the wire 
telegraph. In the wire telegraph about one-hundredth 
horse-power is required to send a message one hundred and 
twenty miles. To send a message the same distance with 
the wireless requires about ten horse-power, or a thousand 
times as much as with the wire telegraph. This is because 
in the wireless telegraph the waves go out in all directions, 
and much of the power is wasted. In the wire telegraph 
the electric waves are directed along the wire and very little 
of the power is wasted. For the same reason a person's 
voice can be heard a long distance through a speaking-tube. 
The speaking-tube guides the sound and prevents it from 
scattering somewhat as the wire guides the electric waves. 

The overhead wires of a wireless-telegraph station send 
out a "dark" light while a message is being sent. (See 
frontispiece.) Standing near the station on a dark night 
one can see nothing, but can hear only the terrific snapping 
of the electric discharge. The camera, however, shows that 
light goes out from the wires. It is light of shorter waves 
than any that the eye can perceive, but the sensitive film 
of the photographic plate makes it known to us. 

The Wireless Telephone 

In sending a message by the wire telegraph the current 
flows over the line wire when the key is pressed. When the 
key is released the current stops. The circuit is made and 
broken for every dot or dash. This we may call an inter- 
rupted current. Now we have seen that the attempt to 
invent a wire telephone using an interrupted current failed. 

221 



THE STORY OF GREAT INVENTIONS 

While one is talking over the wire telephone a current 
(alternating) must be flowing over the line wire. The sound 
of the voice does not make and break the circuit, but 
changes the strength of the current. This alternating cur- 
rent is wonderfully sensitive. It can vary in the rate at 
which it alternates or the number of alternations per second 
to correspond to sound of every pitch. It varies in strength 
to correspond to all the variations in the voice, and repro- 
duces in the receiver not merely the words that are spoken 
but the quality of the voice, so that the voice of a friend 
can be recognized by telephone almost as well as if talking 
face to face. 

The same things are true of the wireless telegraph and 
telephone. Instead of an electric current, let us say "a 
stream of electric waves." Then we may say of the wire- 
less everything that we have said of the wire telegraph and 
telephone. In sending a message by wireless telegraph the 
stream of electric waves flows when the key is pressed and 
stops when the key is released. We have an interrupted 
stream of electric waves. But an interrupted stream of 
waves cannot be used for a wireless telephone any more 
than an interrupted current can be used for a wire-telephone. 
There must be a constantly flowing stream of electric waves, 
and these waves must be changed in strength and form by 
the sound of the voice. Fig. iii shows a wireless-telephone 
receiver in which light is used to carry the message. The light 
acts on the receiver in such a way as to reproduce the sound. 

In the wireless-telegraph receiver the interrupted stream 
of electric waves makes and breaks the circuit of an electric 
battery. The wireless-telephone receiver must not make 

222 



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THE STORY OF GREAT INVENTIONS 



and break a circuit, but it must be sensitive to all the 
changes in the electric waves. One such receiver is the 
audion, which we shall now describe. 

The audion was invented by Dr. Lee de Forest. De 
Forest had taken the degree of Doctor of Philosophy at 
Yale University, having written his thesis for that degree 





Telephone 
receiver 




FIG. 112 A GAS FLAME IS SENSITIVE TO ELECTRIC WAVES 

on the subject of electric waves. He then entered the em- 
ploy of the Western Electric Company in Chicago, and while 
in this position worked at night in his room on experiments 
with electric waves. 

Here he found that a gas flame is sensitive to electric 
waves (Fig. 112). If a gas flame is made part of the circuit 

224 



THE TWENTIETH-CENTURY OUTLOOK 

of an electric battery, which includes also an induction-co'il 
connected to a telephone receiver, then when a stream of 
electric waves comes along there is a click in the receiver. 
The waves change the resistance of the flame, and so change 
the strength of the current. The flame is a simple audion. 
It is the heated gas in the flame that responds to the electric 
waves. 

If instead of a gas flame an incandescent-light bulb is 
used having a metal filament, and on either side of the fila- 
ment a small strip of platinum, a more sensitive receiver is 
obtained. This is the audion, which is the distinguishing 
feature of the De Forest wireless telegraph and wireless 
telephone. The metal filament is made white hot by the 
current from a storage battery. The vacuum in the bulb is 
about the same as that of the ordinary incandescent electric 
light. A very small quantity of gas is therefore left in the 
bulb. The electrified particles of gas respond more freely 
to electric waves in this bulb than in the gas flame. 

The De Forest wireless telephone was adopted for use 
in the United States Navy shortly before the cruise around 
the world in 1908. Every ship in the navy was equipped 
with the wireless telephone, enabling the Admiral to talk 
with the officers of any vessel up to a distance of thirty-five 
miles. The wireless telephone in use on a battle-ship is 
shown in Fig. 113. . 

Wonders of the Alternating Current 

Before the days of the electric current, men used the 
power of falling water. The mill or factory using the water- 

225 



THE STORY OF GREAT INVENTIONS 

power was placed beside the fall. The water turned a great 
wheel, to which was connected the machinery of the mill. 
It was not until the invention of the dynamo and motor 
that water-power could be used at a great distance. If a 




FIG. 113- 



-CAPTAIN INGERSOLL ON BOARD THE U. S. BATTLE-SHIP 
CONNECTICUT" USING THE WIRELESS TELEPHONE 



hundred years ago a man had said that the time would come 
when a waterfall could turn the wheels of a mill a hundred 
miles away he would have been laughed at. Yet this very 



226 



THE T^C^ENTIETH-CENTURY OUTLOOK 

thing has come to pass. Indeed, one waterfall may turn 
the wheels of many factories, run street - cars, and light 
cities up to a distance of a hundred miles and even more. 
The power of the falling water goes out over slender copper 
wires from a great dynamo near the fall to the motors in 
the factories and street-cars. 

The falling water of Niagara has about five million horse- 
power. About the hundredth part of this power is now 
being used. The water, falling in a wheel-pit 141 feet deep, 
turns a great dynamo weighing 87,000 pounds with a speed 
of 250 turns per minute. A number of such dynamos are 
used supplying an alternating current at a pressure of 
22,000 volts, the current alternating or changing direction 
twenty-five times per second. Such a pressure is too high 
for the motors and electric lights, but the current is carried 
at high pressure to the place where it is to be used and 
there transformed to a current of low pressure. In carry- 
ing a current over a long line, there is less loss if the cur- 
rent is carried at high pressure. With an alternating 
current this can be done and the current changed by 
means of a transform^er to a current of low pressure. 

A transformer is simply two coils of wire wound on an 
iron core. The simplest transformer is the form used by 
Faraday when he discovered electromagnetic induction. If 
instead of making and breaking a circuit that flows only in 
one direction as Faraday did, we cause an alternating cur- 
rent to flow through one of the coils, which we may call the 
primary, each time the current changes direction in the 
primary the magnetic field is reversed — that is, the end of 
the coil which was the north pole becomes the south pole. 

227 



THE STORY OF GREAT INVENTIONS 



This rapidly changing magnetic field induces a current in 
the secondary coil. Each time the magnetic field of the 
primary coil is reversed the current in the secondary changes 
direction. Thus an alternating current in the primary in- 
duces an alternating current in the secondary. One of these 
coils is of fine wire, which is wound a great many times 
around the iron. The other is of coarser wire wound only 
a few times around the iron. Suppose the current is to be 
changed from high pressure to low pressure. Then the high- 
pressure current from the line is made to flow through the 
coil of many turns, and a current of low pressure is given out 
from the coil of few turns. By changing the number of 
turns of wire in the coils we can make the pressure whatever 
we please. If the pressure or voltage of the secondary coil 
is less than that of the primary, we have a ** step-down" 
transformer. On the other hand, if we send the current 
from the line wire through the coil of few turns, then we 
get a higher voltage from the secondary coil than that of the 
line wire, and we have a "step-up" transformer. The 
Niagara current is "stepped down" from 22,000 volts to 
220 volts for use in motors. 

An electric lamp may be lighted though not connected to 
any battery or dynamo, but connected only to a coil of 
wire (Fig. 114). More than this, the coil may be insulated 
so that no current can enter it from any other coil or wire, 
and yet the lamp can be lighted. This can be done only by 
means of an alternating current. If the coil to which the 
lamp is connected is held in the magnetic field of an alter- 
nating current, then another alternating current is induced 
in the coil, and this second current flows through the lamp. 



THE TWENTIETH-CENTURY OUTLOOK 




FIO. 114- 



-INCANDESCENT ELECTRIC LAMP LIGHTED THOUGH NOT CON- 
NECTED TO ANY BATTERY OR DYNAMO 



We have already learned that a changing magnetic field in- 
duces a current in a coil. Now the coil through which an 
alternating current is flowing has a changing magnetic field 
all around it, and if the lamp-coil is brought into this 
changing magnetic field an alternating current will flow 
through the coil and the lamp. The insulation on the 
lamp-coil does not prevent the magnetic field from acting, 

229 



THE STORY OF GREAT INVENTIONS 

though it does prevent a current from entering the coil. 
The current is induced in the coil itself, and does not enter 
it from any outside source. 

The transformer works in the same way, the only differ- 
ence being that in the transformer the two coils are on the 



M:^ 



AN ELECTRIC DISCHARGE AT A PRESSURE OF T2, 000,000 VOLTS, 
A CURRENT OF 8oO AMPERES IN THE SECONDARY COIL 



same iron core. But in the transformer the two coils are 
insulated so that no current can flow from one coil to the 
other. When an alternating current and transformers are 
used, the current that lights the lamps in the houses or on 
the streets is not the current from the dynamo. It is a new 

230 



THE TWENTIETH-CENTURY OUTLOOK 

current induced in the secondary coil of the transformer by 
the magnetic field of the primary coil. 

A peculiar transformer which produces an alternating 
current that changes direction millions of times in a second 
has been made by Nikola Tesla. This current will do many 
wonderful things which no ordinary current will do. It 
will light a room or run a motor without connecting 
wires. It has produced an electric discharge sixty -five 
feet in length (Figs. 115 and 116). Though this current 
is caused to flow by a pressure of millions of volts, it may 
be taken with safety through the human body. Strange as 
it may seem, the safety of this current is due to the high 




FIG, 116. — \N ELECTRIC DISCHARGE SIXTY-FIVE FEET IN LENGTH 

231 



THE STORY OF GREAT INVENTIONS 

pressure and the rapidity with which it changes direction. 
While the current used at Sing Sing in executing criminals 
has a pressure of about twenty-five hundred volts, a current 
having a pressure of a million volts and alternating hundreds 
of thousands or millions of times per second is harmless. 
With such a current the human body may become a ''live 
wire," and an electric lamp to be lighted held in one hand 
while the other hand grasps the wire from the transformer. 

X-Rays and Radittm 

A strange light which passes through the human body as 
readily as sunlight through, a window was discovered by 
Prof. Wilhelm Konrad Roentgen, of the University of Wurz-_ 
burg. This light, which Professor Roentgen named X-rays, 
is given out when an electric discharge at high pressure 
passes through a certain kind of glass tube from which the air 
has been pumped out until there is a nearly perfect vacuum. 

X-rays were discovered by accident. Professor Roentgen 
was working at his desk with one of the glass tubes when 
he was called to lunch. He laid the tube with the electric 
discharge passing through it on a book. Returning from 
lunch he took a photographic plate-holder which was under 
the book and made some outdoor exposures with his 
camera. On developing the plates a picture of a key ap- 
peared on one of them. He was greatly puzzled at first, 
but after a search for the key found it between the leaves 
of the book. The strange light from the electric discharge 
in the glass tube had passed through the book and the hard- 
rubber slide of the plate-holder and made a shadow-picture 




FIG. 117 A PHYSICIAN 



EXAMINING THE BONES OF THE ARM BY MEANS 
OP X-RAYS 



THE STORY OF GREAT INVENTIONS 

of the key on the photographic plate. He tried the strange 
Hght in many ways, and found that it would go through 
many objects. It would even go through the human body, 
so that shadow-pictures of the bones and organs of the 
body could be obtained. In Fig. 117 is shown a physician 
using X-rays. Fig. 118 is an X-ray photograph of the eye. 




X-RAY PHOTOGRAPH OF THE EYE 



The eye is above and to the left of the larger black circle, 
black circle is a shot which has lodged back of the eye. 



The smaller 



Not long after the discovery of X-rays it was discovered 
that light very much like the X-rays is given out by certain 
minerals. One of the most interesting and the best known 
of these is radium. Radium gives out a light somewhat 
like X-rays that will go through copper and other metals. 
It does many other strange things. It gives out heat as 

234 



THE TWENTIETH-CENTURY OUTLOOK 



well as light; so much heat, in fact, that it is always about 
five degrees warmer than the air around it. It continues 
to give out heat at such a rate that a pound of radium will 
melt a pound of ice every hour. It can probably keep this 
up for at least a thousand years. If this heat could be 
used in running an engine, a hundred pounds of radium 
would run a one-horse-power engine without stopping for 
many hundred years. The power of Niagara might be re- 
placed by the power of radium if an engine that could use 
this power were invented. Fig. 119 is from a photograph 
made with radium. 




FIG. 119 PHOTOGRAPH MADE WITH RADIUM 

A purse containing a coin. The strange light from the radium goes 
through the purse and the slide of the plate-holder and makes a shadow- 
picture. 

235 



THE STORY OF GREAT INVENTIONS 

The great inventor of the future may be able to use the 
heat of radium or some new power now unknown. We 
have seen how, through the toil of many years and the 
labors of many men, the great inventions of our age have 
come into being. It may be that we are now witnessing 
other great inventions in the making. 



APPENDIX 

BRIEF NOTES ON IMPORTANT INVENTIONS 

Aerial Navigation 

FIRST air balloon — Montgolfier Brothers, France, 1783. 
First balloon ascension — Rozier, France, 1783, 
First gas balloon — Charles, France, 1783. 

First crossing of the English Channel in a balloon — Blanchard, 1785. 
First successful dirigible balloon — La France, Renard and Krebs, 
France, 1884. 
/'First successful motor-driven aeroplane — Wright Brothers, United 

States; date of patent, 1906. ^ 
^ First crossing of the English Channel by an aeroplane — Bleriot, 1909. 
//First air-ship in regular passenger service — Count Zeppelin, Ger- 
many, 19 10. 

Agricalttire 

Plough with cast-iron mold-board and iron shares — James Small, 
Scotland, 1784. 

Grain- threshing machine — Andrew Meikle, England, 1788. 

McCormick reaper, first practical grain - harvesting machine — 
Cyrus H. McCormick, United States, 1831. 

Self -raker for harvesters — McCormick, 1845. 

Inclined platform and elevator in the reaper, to enable men bind- 
ing the grain to ride with the machine — J. S. Marsh, United 
States, 1858. 

Barbed-wire fence introduced — United States, 1861. 

Self-binder, first automatic grain-binding device for the reaper — 
Jacob Behel, United States, 1864. 

Sulky plough — B. Slusser, United States, 1868. 

237 ,, 



THE STORY OF GREAT INVENTIONS 

Twine-binder for harvesters — M. L. Gorham, United States, 1873. 
Improved self -binding reaper — Lock and Wood, United States, 1873. 
Barbed-wire machine — Glidden and Vaughn, United States, 1874. 
Rotary disk cultivator — Mallon, United States, 1878. 
Steam-plough — W. Foy, United States, 1879. 

Combined harvester and thresher — Matteson, United States, 1886. 
Automobile mower — Deering Harvestor Company, United States, 
1901. 

Atttomobilc 

First steam-automobile — Cugnot, France, 1769. 

First chain transmission of power in an automobile — Gurney, 
England, 1829. 

Application of gas-engine to road vehicles, beginning of the modern 
motor-car — Gottlieb Daimler and Carl Benz working independ- 
ently, Germany, 1886. Daimler's invention consisted of a 
two-cylinder air-cooled motor. It was taken up in 1889 ^Y 
Panhard and Levassor, of Paris, who began immediately the 
construction of the motor-car. This was the beginning of the 
motor-car industry. 

Bicycle 

First bicycle — Branchard and Magurier, France. 1779. 
Rear-driven chain safety bicycle — George W. Marble, United States, 

1884. 
Bicycles first equipped with pneumatic tires — 1890 

Electrical Inventions 

William Gilbert, England, 1540-1603, called "the father of magnetic 
philosophy," first to use the terms "electric force," "electric 
attraction," "magnetic pole." 

First electrical machine, a machine for producing electricity by 
friction — Otto von Guericke, Germany, about 1681. 

Discovery of conductors and insulators — Stephen Gray, England, 
1696-1736. 

First to discover that electric charges are of two kinds — Cisternay 
du Fay, France, 1698-1739; Du Fay was also the first to at- 
tempt an explanation of electrical action. He supposed that 
electricity consists of two fluids which are separated by friction, 

238 



APPENDIX 



and which neutralize each other when they combine. This 
theory was more fully set forth by Robert Symmer. 

Leyden jar — Discovered first by Von Kleist in 1745. The same 
discovery was made and the Leyden jar brought to the atten- 
tion of the public in 1 746 by Pieter van Musschenbroek in Holland. 

Lightning-rod — Benjamin Franklin, 1732. 

Electroplating — Luigi Brugnatelli, Italy, 1805. 

Voltaic arc, a powerful arc light produced with a battery current — 
Sir Humphry Davy, England, 1808. 

Storage battery — Ritter, Germany, 1803. Platinum wires were 
dipped in water and a battery current passed through. Hydro- 
gen collected on one wire and oxygen on the other. If the 
platinum wires were disconnected from the battery and con- 
nected with each other by a conductor, the two wires acted 
like the plates of a battery, and a current would flow for a short 
time in the new circuit. 

Electromagnet ism discovered — H. C. Oersted, Denmark, 18 19. 

Galvanometer, a coil of wire around a magnetic needle for measur- 
ing the strength of an electric current — Schweigger, Germany, 
1820. 

Motion of magnet produced by an electric current — M. Faraday, 
England, 182 1. 

Thermo-electricity, an electric current produced by heating' the 
junction of two unlike metals — Discovered by Professor See- 
beck, England, 182 1. 

Principles of electrodynamics, motion produced by an electric cur- 
rent — Ampere, France. Announced in 1823. 

Law of electric circuits. Ohm's law, current strength equals electro- 
motive force divided by resistance of the circuit — George S. 
Ohm, Germany. Proven by experiment in 1826 ; mathematical 
proof published in 1827. 

Magneto-electric induction, induction of electric currents by means 
of a magnetic field — M. Faraday, England, 183 1. 

Electric telegraph — Prof. S. F. B. Morse, United States, 1832. 

First telegram sent in 1844 — Morse. 

Constant electric battery — J. P. Daniell, England, 1836. 

First electric motor-boat — Jacobi, Russia, 1839. 

Induction-coil — Rhumkorff, Germany, 185 1. 

Duplex telegraph, first practical system — Stearns, United States, 
about 1855-1860. 
16 239 



THE STORY OF GREAT INVENTIONS 

Storage battery, lead plates in sulphtiric acid — Gaston Plante, 
France, 1859. 

Telephone, make-and-break system, first electrical transmission of 
speech — Philip Reiss, Germany, i860. 

Atlantic cable laid — Cyrus W. Field, 1866. 

Dynamo, armature coil rotates in the field of an electromagnet, 
armature supplies current for the electromagnet as well as 
for the external circuit — William Siemens, Germany, 1866. 

Gramme ring armature for dynamo — Gramme, France, 1868. 

Theory that light consists of electromagnetic waves — Clerk-Max- 
well, England, 1873. 

Quadruplex telegraph, sending four messages over one wire at the 
same time — Edison, 1873. 

Siphon recorder for submarine telegraph, sensitive to very feeble 
currents — Sir William Thomson, England, 1874. 

Telephone, varying current, first practical working telephone — 
Alexander Graham Bell, United States, 1876. 

Electric candle, beginning of present arc light — Paul Jablochkoff, 
Russia, 1876. 

Telephone transmitter of variable resistance — Em.il Berliner and 
Edison working independently, United States, 1877. Edison 
used carbon contacts, Berliner used metal contacts. 

Brush system of arc lighting^i878. 

Incandescent electric lamp with carbon filament — Edison, 1878. 

First electric locomotive — Siemens, Germany, 1879. 

Blake telephone transmitter — Blake, United States, 1880. 

Storage battery, lead grids filled with active material — Faure, 
France, 1881. 

Electric welding — Elihu Thompson, United States, 1886. 

Electric waves discovered by experiment — Heinrich Hertz, Ger- 
many, 1888. 

Coherer for receiving electric waves — Edward Branly, France, 
1890. 

X-rays — Discovered by Prof. W. C. Roentgen, Germany; announced 
to the public in 1895. 

Wireless telegraphy — G. Marconi, Italy, 1896. 

Nernst electric light, a clay capable of conducting electricity when 
heated is used; it becomes incandescent without a vacuum — 
Walter Nernst, Germany, 1897. 

Radium discovered by Madame Curie, France, 1898. 

240 



APPENDIX 



/ 



Explosives 

Gunpowder — Inventor and date unknown. 
Guncotton — Schonbein, Germany, 1845. 
Nitroglycerine — Sobrero, 1847. 
Explosive gelatine — A. Nobel, France, 1863. 
Dynamite — A Nobel, France, 1866. 
Smokeless powder — Vielle, France, 1866. 

Firearms and Ordnance 

Spirally grooved rifle barrel — Koster, England, 1620. 

Breech-loading shot-gun — Thornton and Hall, United States, 181 1. 

The revolver; a device "for combining a number of long barrels 
so as to rotate upon a spindle by the act of cocking the ham- 
mer" — Samuel Colt, United States, 1836. 

Breech gun-lock, interrupted thread — Chambers, United States, 1849. 

Magazine gun — Walter Hunt, United States, 1849. 

Breech-loading rifle — Maynard, United States, 185 1. 

Iron-clad floating batteries first used in Crimean War — 1855. 

Breech-loading ordnance — Wright and Gould, United States, 1858. 

Revolving turret for floating batteries — Theodore Timby, United 
States, 1862. 

First iron-clad floating battery propelled by steam: the Monitor — 
John Ericsson, United States, 1862. 

Gatling gun — Dr. R. J. Gatling, United States, 1862, 

Automatic shell-ejector for revolver — W. C. Dodge, United States, 
1865. 

Torpedo — Whitehead, United States, 1866. 

Disappearing gun-carriage — Moncrief, England, 1868. 

Rebounding gun-lock — L. Hailer, United States, 1870. 

Magazine rifle — Lee, United States, 1879. 

Hammerless gun — Greener, United States, 1880. 
^ Gun silencer, to be attached to barrel of gun; gun can be fired 
/ without noise — Maxim, 1909. 

Gas Used for Light and Power 

Gas first used for illuminating purposes — William Murdoch, England, 

1792. 
First street gas-lighting in England — F. A. Winsor, 18 14. 

241 



THE STORY OF GREAT INVENTIONS 

Gas-meter — S. Clegg, England, 1815. 

Water-gas, prepared by passing steam over white-hot anthracite 

coal — First produced in England in 1823. 
Illuminating water-gas — Lowe, United States, 1875. 
Gas-engine, 4-cycle, beginning of modern gas-engine — Otto and 

Langen, Germany, 1877. 
Incandescent gas-mantle — Carl A. von Welsbach, Austria, 1887. 

Iron and Steel 

Blast-furnace, beginning of iron industry — Belgium, 1340. 

Use of coke in blast - furnace — Abram Darly, England, about 
1720, 

Puddling iron — Henry Cort, England, 1783-84. 

Process of making malleable-iron castings — Lucas, England, 1804. 

Hot-air blast for iron furnaces — J. B. Neilson, Scotland, 1828. f 

The galvanizing of iron — Henry Craufurd, England, 1837. v 

Process of making steel, blowing air through molten pig-iron to 
bum out carbon, then adding Spiegel iron; first production of 
cheap steel — Sir Henry Bessemer, England, 1855. 

Regenerative furnace, a gas - furnace in which gas and air are 
heated before being introduced into the furnace, giving an 
extremely high temperature — William Siemens, England, 
1856. 

Open-hearth process of making steel — Siemens-Martin, England, 
1856. 

Nickel steel, much stronger than ordinary steel, used for armor- 
plate — Schneider, United States, 1889. 

Mining 

Miners' safety-lamp — Sir Humphry Davy, England, 1815. 

Compressed-air rock-drill — C. Burleigh, United States, 1866. 

Diamond rock-drill, a tube of cast-steel with a number of black 
diamonds set at one end. The machine cuts a circular groove, 
leaving a core inside the tube. This core is brought to the 
surface with a rod, and the powdered rock is washed out by 
water forced down the tube and flowing up the sides of the 
hole. The drill does not have to stop for cleaning out — Her- 
man, United States, 1854. 

242 



APPENDIX 



Photography 

First photographic picture, not permanent — Thomas Wedgewood, 

England, 1791. 
Daguerreotype, first developing process — Louis Daguerre, France, 

1839. 
First photographic portraits, daguerreotype process — Prof. J. W. 

Draper, United States, 1839. 
Collodion process in photography — Scott Archer, England, 1849. 
Photographic roll films — Melhuish, England, 1854. 
Dry -plate photography — Dr. J. M, Taupenot, 1855. 
Photographic emulsion, bromide of silver in gelatine, basis of 

present rapid photography — R. L. Maddox, England, 187 1. 
Hand photographic camera for plates — William Schmid, United 

States, 1 88 1. 

Printing 

First printing with movable types in Europe and first printing- 
press — Guttenberg, Germany, about 1445. 

Screw printing-press — Blaew, Germany, 1620. 

First newspaper of importance — London Weekly Courant, 1625. 

Stereotyping, making plates from casts of the type after it is set 
up — William Ged, Scotland, 1731. 

First practical steam rotary printing-press, paper printed on both 
sides, 1800 impressions per hour — Frederick Koenig, Ger- 
many, 1 8 14. 

Printing from curved stereotype plates — H. Cowper, England, 181 5. 

Hoe's lightning press, 2000 impressions per hour — R. Hoe, United 
States, 1847. 

Printing from a continuous web, paper wound in rolls, both sides 
printed at once — William Bullock, United States, 1865. 

" Straightline newspaper perfecting" press, prints 100,000 eight- 
page papers her hour — Goss Company, United States. 

Linotype machine. The operator uses a keyboard like that of a 
typewriter. The machine sets the matrices which correspond 
to the type, casts the type in lines from molten metal, delivers 
the lines of type on a galley, and returns the matrices to their 
appropriate tubes. It does the work of five men setting type 
in the ordinary way — Othmar Mergenthaler, United States, 
1890. 

243 



THE STORY OF GREAT INVENTIONS 

Steam Navigation 

First steamboat in the world — Papin, River Fulda, Germany, 1705. 
First steamboat in America— John Fitch, Delaware River, 1783. 
First passenger steamboat in the world, the Clermont — Robert 

Fulton, Hudson River, 1807. 
First steamer to cross the Atlantic, the Savannah, built at New York 

— First voyage across the Atlantic, 18 19. 
The screw propeller first used on a steamboat — John Ericsson, 

United States, about 1836. 
Compound engines adopted for steamers — 1856. 
First turbine-steamer, the Turhinia — Parsons, 1895. 
First mercantile steam-turbine ship, the King Edward — Denny and 

Brothers, England, 1901. 

Steam Used for Power and Land Transportation 

First steam-engine with a piston — Denys Papin, France, 1690. 

First practical application of the power of steam, pumping water — 
Thomas Savery, England, 1698. 

Double-acting steam-engine and condenser — James Watt, Scotland, 
1782. 

Steam-locomotive first used to haul loads on a railroad — Richard 
Trevethick, England, 1804. 

First passenger steam railway, the "Stockton & Darlington" — 
George Stephenson, England, 1825. 

First steam - locomotive in the United States, the "Stourbridge 
Lion" — 1829. 

Link motion for locomotives — George Stephenson, England, 1833. 

Steam- whistle, adopted for use on , locomotives — George Stephen- 
son, 1833. 

Steam-hammer — James Nasmyth, Scotland, 1842. 

Steam-pressure gauge — Bourdon, France, 1849. 

Corliss engine— G. H. Corliss, United States, 1849. 

First practical steam-turbine — C. A. Parsons, England, 1884. 

Textile Industries 

Flying shuttle, first important invention in weaving, leading to 
modern weaving machinery — John Kay, England, 1733. 

244 



APPENDIX 



Spinning-jenny — James Hargreaves, England, 1763. 

Power loom — James Cartwright, England, 1785. 

Cotton-gin, for separating the seeds from the fibre, gave a new 

impetus to the cotton industry. The production of cotton 

increased in five years from 35,000 to 155,000 bales — Eli 

Whitney, United States, 1792. 
Pattern loom, for the weaving of patterns — M. J. Jacquard, France, 

1801. 
Application of steam to the loom — William Horrocks, England, 

1803. 
Knitting-machine — Brunei, England, 1816. 
Sewing-machine— Elias Howe, United States, 1846. 
Mercerized cotton — John Mercer, England, 1850. 
Process of making artificial silk — H. de Chardonnet, France, 1888. 

Wood-Working 

Circular wood-saw — Miller, England, 1777. 

Wood-planing machine — Samuel Benthem, England, 1791. 

Wood-mortising machine — M. J. Brunei, England, 1801. 

Band wood-saw — Newberry, England, 1808. 

Lathe for turning irregular wood forms — Thomas Blanchard, United 

States, 1819. 
Improved planing-machine — William Woodworth, United States, 

1828, 

Miscellaneotis 

First fireproof safe — Richard Scott, England, 180 1. 

Steel pen, quill pen used xxp to this time — Wise, England, 1803. 

First life-preserver — John Edwards, England, 1805. 

Calculating machine — Charles Babbage, England, 1822. 

First friction matches — John Walker, United States, 1827, Flint 
and steel were used for starting fires before matches were 
invented. 

First portable steam fire-engine — Brithwaite and Ericsson, Eng- 
land, 1830. 

Vulcanizing of rubber — Charles Goodyear, United States, 1839. 

Pneumatic tire — R. W. Thompson, England, 1845. 

Time-lock for safes — Savage, United States, 1847. 

Match-making machinery — A. L. Denison, United States, 1850. 

245 



THE STORY OF GREAT INVENTIONS 

American machine-made watches — United States, 1850. 

Safety matches — Lundstrom, Sweden, 1855. 

Sleeping-car — Woodruff, United States, 1856, 

Printing-machine for the blind, origin of the typewriter — Alfred E. 
Beach, United States, 1856. 

Cable-car — E. A. Gardner, United States, 1858. 

Driven well, an iron tube with the end pointed and perforated 
driven into the ground — Col. N. W. Green, United States, 186 1. 

Passenger elevator — E. G. Otis, United States, 1861. 

First practical typewriter — C. L. Sholes, United States, 186 1. 

Railway air-brake, use of air-pressure in applying brakes to the 
wheels of a car. A strong spring presses the brake against 
the wheels. Air acts against the spring and holds the brake 
away from the wheels. To apply the brake, air is allowed to 
escape, reducing the pressure and allowing the spring to act — 
George Westinghouse, United States, 1869. 

Store-cash carrier — Dr. Brown, United States, 1875. 

Roller flour-mills — F. Wegman, United States, 1875. 

Kinetoscope, moving-picture machine — Edison, 1893. 



INDEX 



Aeroplane, 184. 

Air-pressure, 23. 

Air-pump, 20. 

Air-ships, 173. 

Air thermometer, 13. 

Alternating current, wonders of, 

225. 
Amber, 8. 
Ampere, 67, iii. 
Arago, 69. 

Archimedes, i, 12; inventions of, 7. 
Archimedes' principle, 6, 12. 
Arc light, 120. 
Armature, loi, 103, 104. 

Balloons, 174. 

Barometer, mercury, 19, 25; water, 

23- 
Battle of Syracuse, 2. 
Bell, Alexander Graham, 141. 
Blake transmitter, 146. 
Bleriot, 190. 
Boyle, 23. 
Branly, 214. 

Cannon EXPERIMENT, Rumford's, 59. 
Cog-wheels, first used, 8. 
Coherer, 214. 
Colors in sunlight, 31. 
Condenser in steam-engine, 40. 
Conductors, electrical, 44. 
Controller, 116. 

Daniell cell, 89, 127. 
Davy, 56, 61, 96. 
De Forest, 224. 



Diamonds, manufacturing, 206. 

Drum armature, 104. 

Dry battery, 91. 

DuFay, 45. 

Dumont, 179. 

Duplex telegraphy, 136. 

Dynamo, 55, 79, 81, 96, 99, 100, 
105, in; series wound, 105 ; shunt 
wound, 107; compound wound, 
108. 

Edison, 95, 105, 114, 121. 
Electrical machine, 23, 44, 45, 83. 
Electric battery, 53, 62, 84, 89. 
Electric charge, two kinds, 45. 
Electric current, 50, 69, 73, 74, 82, 

96; magnetic action of, 66, 68; 

produced by a raagnet, 72. 
Electric furnace, 205. 
Electricity, 8, 50; theories of, 49; 

speed of, 133. 
Electric lighting, 97, 118. 
Electric motor, 71, 97, in. ^ 

Electric power, in. 
Electric railway, 112. 
Electric waves, 212. 
Electromagnet, 100, 126, 143. 
Electromagnetism, 65. 

Faraday, 55, 63, 100, in; elec- 
trical discoveries, 64. 
Force-pump, 8. 
Franklin, 43, 45, 46, 65. 

Galileo, 9, 63 ; experiment with 
falling shot, 12. 



247 



THE STORY OF GREAT INVENTIONS 



Galvani, 50. 
Galvanometer, 74, 75. 
Gas-engines, 150. 
Glider, 186. 
Governor, fly -ball, 42. 
Gramme-ring armature, 103. 
Gravitation, 30. 
Gravity cell, 91. 
Gray, Stephen, 44. 
Guericke, 20, 35. 
Gyroscope, 200. 

Heat, 59. 

Henry, Joseph, 97, 127. 

Hero, 8, 164; engine, 164. 

Hiero, King of Syracuse, i, 6. 

Horse-power, 40. 

Hydraulic press, 26. 

Incandescent light, 121. 
Indicator, 41. 
Induction-coil, 76, 82, 99. 
Induction, electrical, 74. 
Insulators, 44. 

Inventions of the ancient Greeks, 
7; of the nineteenth century, 88. 

Kite experiment, Franklin's, 46. 
Kites, 27. 

Leyden jar, 43. 

Lightning-rod, 48. 

Lines of force, 99. 

Liquid air, 203. 

Locomotive, electric, 114; steam, 155. 

Magdeburg, 21. 
Magnetic field, 80, 99. 
Magnets, 8, 130. 
Marconi, 215. 
Mayer, Robert, 61, 85. 
Mercury vapor light, 125. 
Microscope, 18. 
Miner's safety lamp, 61. 
Monorail car, 201. 
Morse, 128. 

Napoleon, 62. 
Newcomen, 34, 36. 
Newcomen's engine, 36. 



Newton, 27. 
Niagara, 227 

Oersted, 65, 71, m, 126. 

Papin, 35. 

Papin's engine, 35. 

Pascal, 25. 

Pendulum clock, 10, 12, 

Perpetual motion impossible, 87. 

Phonograph, 147. 

Principle of work, 19. '" 

Prism, 31. 

Pump, 8, 19. 

Radium, 232. 

Reis, Philip, 141. 

Relay, 130. 

Roentgen, 232. 

Royal institution, 56, 61. 

Rumford, 57, 59. 

Rumford's cannon experiment, 59. 

Safety-lamp, 62. 
Screw propeller, 171. 
Siemens', 100. 
Spinning tops, 199. 
Steam-engine, 8, 25, 34. 
Steam locomotive, 155. 
Steam pressure, 23. 
Stephenson, 156. 
Storage battery, 93, 
Sturgeon, 97, 127. 
Submarines, 190. 
Suction-pump, 8. 
Symmer, Robert, 49. 

Telegraph, 96, 126; wireless, 208. 
Telephone, 140; wireless, 221. 
Telescope, invention of, 15; New- 
ton's 32,. 
Tesla, 231. 

Thermometer, air, 13. 
Torpedo, 192. 
Torricelli, 19, 35. 
Transformer, 80, 82, 99, 227. 
Turbine, 1 63 . 

University of Padua, 13. 
University of Pisa, 10, 12. 

48 



Valve-gear, 37, 162. 
Volta, 53, 63, 89. 
Voltaic battery, 53, ^ 

Water-clock, 8, 29, 
Water-wheel, 165. 
Watt, James, 34. 



INDEX 



Watt's engine, 38. 
Wireless telegraph, 20^ 
Wright aeroplane, 188. 

X-RAYS, 232. 

Zeppelin. 180. 



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